The aim of the investigation is to portray a composite picture of the native and non-native expert and novice writers composing and revising processes as they wrote an argumentative essay in English. Analyses of the experienced and novice writers revision processes served to answer four main questions posed at the beginning of the experimental study: 1. When did revisions occur during the composing process? 2. Were there any similarities and differences in the categories of revision the subjects employed? 3. Were there any similarities and differences in the techniques the subjects employed? and 4. Were there any similarities and differences in the purposes of the subjects revisions? These questions were also posed to compare the native and nonnative expert writers and the native and non-native novice writers. The results indicate that the native and non-native experienced and novice writers in this study made changes in the first and second writing sessions, in the four writing cycles, and in the combinations pre-draft/first draft and between draft/final draft, although they revised to different extends. Both writer groups coincided in their preference for the word level over the surface, phrase, clause, sentence, paragraph and global levels. The experienced subjects, however, revised at the higher discourse levels more often than the novice writers did. No important differences were concluded between both writer types in the techniques used for revising. Per purposes of revision, both the expert and novice writers revised with an informational purpose in mind, although they differed in their preference for the rest of purposes of revision: while the expert writers made higher proportions of meaning revisions, the novice showed a tendency for formal changes. Further comparisons indicate there were also similarities between both types of writers: the unskilled writers in this study were also aware of the need for making content revisions. Indeed, they made some attempts at improving meaning through sentence, paragraph and global revisions, although they failed to achieve success. The native and non-native experienced subjects coincided in their preference for the word level across drafts and writing sessions. The rest of the levels occurred in descending order as the discourse level ascended from the word to the global level. Global changes were often avoided as they needed more cognitive effort. They also showed interest for the surface level, although they seemed to have the cognitive ability to manage form and content at the same time. Additions and substitutions of information prevailed over the rest, since the writers hardly ever deleted to start again. Despite the similarities between the native and non-native expert writers, further comparisons reveal that the native expert subject showed more concern with meaning, while the non-native were worried about grammatical correctness, which may be due to the greater emphasis that they receive in L2 writing classes. Also, the subjects displayed different revision patterns, which supports the belief that there is no single revision pattern resulting in successful prose. The native novice subjects made higher percentages of final version revisions, while the non-native were more inclined to making premature revisions, coupled with large numbers of revisions in an attempt to reduce the cognitive load that revising entailed on their minds. The pre-draft, between-draft and the combinations of drafts were virtually of no importance and, thus, the writers did not go back and forth between their essays and outlines to add changes or to check how well the drafts matched their outlines. Yet, both writer types redirected their attention to meaning towards the latest stages of writing and, therefore, they were not insensitive to revision at the higher discourse levels, contrary to the beliefs commonly held for novice writers. __________________________________________________________________________________________________ RESUMEN El objetivo de esta investigación es describir los procesos de escritura y aprendizaje de escritores nativos y no nativos expertos e inexpertos mientras escribían un texto argumentativo en inglés. El análisis de los procesos de revisión de los escritores experimentados y menos experimentados sirven como punto de partida para contestar cuatro preguntas principales: 1. ¿Cuándo se dan las revisiones en el proceso de escritura? 2. ¿Hay similitudes y diferencias en las categorías de revisión que los participantes usaron? 3. ¿Hay similitudes y diferencias en las técnicas que los participantes emplearon? 4. ¿Hay similitudes y diferencias en los propósitos de las revisiones de los participantes? Estas mismas preguntas se plantearon para observar las similitudes y diferencias entre los escritores experimentados nativos y no nativos y entre los escritores no experimentados nativos y no nativos de inglés. Los resultados indican que los escritores expertos y no expertos nativos y no nativos de este estudio hicieron cambios en las dos sesiones de escritura, en los cuatro ciclos de escritura, así como en las combinaciones guion/primer borrador y borrador intermedio/borrador final aunque revisaron en diferente medida. Los escritores experimentados, sin embargo, revisaron a niveles discusivos más altos con más frecuencia que los menos experimentados, aunque los menos expertos no son completamente inconscientes de la necesidad de hacer revisiones de significado. Los escritores experimentados y menos experimentados nativos y no nativos coincidieron en su preferencia por la revisión a nivel de la palabra en todos los borradores y sesiones de escritura. No hicieron cambios que afectaran la estructura global del texto puesto que implicaban un mayor esfuerzo cognitivo. A pesar de las similitudes los escritores expertos nativos mostraron un mayor interés por el significado, mientras los no nativos se preocuparon de la corrección gramatical de sus textos. Los escritores nativos no expertos hicieron un mayor número de revisiones en el borrador final que los no nativos menos experimentados, mientras éstos revisaron en fases demasiado avanzadas del proceso de escritura además de hacer un gran número de ellas en un intento de reducir la carga cognitiva que revisar imponía en sus mentes. Ambos se centraron en la comunicación de significado en las fases finales de escritura.