A study of individual variability in second-language learners' performance in specific classroom tasks is presented as evidence that instruction in language for special purposes (LSP) has an important role to play. Subjects were 17 Singapore university students in a remedial English course; all had studied English since elementary school. The subjects performed four tasks: a language test; an essay; an interview; and a peer-group discussion. Performance on each tasks was analyzed for patterns of use of simple present, simple past, and present perfect tenses. Accuracy rates reflect variability in use of the tenses. Results indicate that the accuracy rate was highest for the discussion tasks, and lower for essay, interview, and language test, in descending order of accuracy. These figures suggest that use of tense/aspect varies across tasks. Further, contextual analysis of task performance looked at verb usage within four categories of context (verbal aspect, adverbials, serialization, implicit reference) for each task type. The verbal aspect category was found most problematic, followed by adverbials, serialization, and implicit reference in descending order. Overall, results indicate that context influences task accuracy rate, suggesting that LSP, which is context-based, is an important way to teach second languages. (MSE)