A study tested the hypothesis that spoken language has a strong direct influence on the encoding process, and that speakers of nonstandard dialects have a different set of problems with the written language and make identifiably different errors than do speakers of standard dialect. The subjects, 13 standard and 13 nonstandard dialect speakers enrolled in adult basic writing courses, completed a variety of writing tasks in different discourse modes as well as tasks involving oral language. Errors were counted and categorized as follows: those not linguistically based, but rather "ignorant" or perceptual in origin; those that might be explained as nonlinguistic or linguistic in origin; those that were unambiguously linguistic in origin; and those noted but not counted. Results indicated that, among adult basic writers (1) differences in reading comprehension skills seemed not to account for differences in total quantities of errors or for differences in types of errors committed; (2) such is the overriding influence of nonstandard dialect on encoding behavior, that even when composing and cognitive skills were on the same level, nonstandard dialect speakers were likely to produce many more errors than were standard dialect speakers; and (3) nonstandard speech patterns apparently accounted for two highly stigmatized categories of errors--hypercorrect linguistic forms and wrong whole-word verb forms--and for a large portion of omitted inflectual suffixes. (Materials used in the study are appended.) (FL)