In this paper we show that supplying positive evidence in the second language (L2) classroom does not necessarily trigger the appropriate L2 value of a parameter of Universal Grammar. The parameter we investigate is the verb movement parameter of Pollock (1989), which accounts for the fact that English and French adverbs differ as to where they occur in relation to the verb: In French the verb raises past the adverb, allowing the order SVAO but not SAV, whereas in English the verb does not raise, allowing SAV but not SVAO. Fifty-four francophone children (aged 11) in intensive English-as-a-second-language programs in Quebec, Canada, were exposed to a 2-week input flood of specially prepared materials containing English adverbs used naturalistically. No form-focused instruction or negative evidence on adverb placement was provided. Subjects were pretested immediately prior to the input flood, posttested immediately afterward, and again 3 weeks later, on four different tasks. On all tasks there is a change between pretest and posttest behavior, namely, a dramatic increase in use of the English SAV order but little or no decline in incorrect usage of SVAO. Results are also compared to groups reported in White (1991a, 1991b); the subjects in the present study differ from both groups in the previous studies. The results of the present study suggest that positive evidence does not serve to preempt the first language parameter setting in this case; acquiring the correct English SAV order did not lead to loss of incorrect SVAO. Implications of this result for theories of preemption and parameter setting in L2 acquisition are discussed.