A young Spanish woman was given 82 hours of individual instruction in English. Her exposure to and use of English were confined to these lessons. The subject acquired adjective-noun ordering and regular plural relatively quickly; possessor-possessed ordering and genitive relatively slowly; the definite article all at once after a period of omitting it; and third person "s" not at all. An analysis of the results indicates: (1) the importance of frequency in acquisition; (2) poorer performance when novel word combinations are attempted; (3) the unhelpfulness of the competence-performance distinction in the description of learners' language; (4) the strength of interference even when error-free learning has taken place; (5) the interaction of various factors in the production of individual errors, which typical cross-sectional data would be unlikely to reveal; and (6) support for the notion that all untutored learners of a language will in the early stages pidginize it in order to communicate. Data are graphically presented. (Author/JB)