Previous research has shown that sequences in which instances from the same category appear successively facilitate performance in concept attainment. This could be due to subjects adopting strategies which involve comparisons of instances from within the same category. However, if subjects were to adopt a strategy involving comparisons of instances from different categories, a sequence involving maximum contiguity of instances from the same category would be nonfacilitating and, very likely, detrimental to concept attainment. For this study, subjects were trained to solve the concept task by comparing instances from the same or different categories. A control group received no instructions on how to solve the task. The three instructional groups were factorially combined with two types of sequences (one favoring within-category comparisons and one favoring across-category comparisons) and two different dimensions relevant to the category. Results showed a significant interaction between strategy and type of sequence, indicating that differently structured sequences can cause differences in performance but these differences depend on the subject's strategy. (Author/SH)