Mandler (1969) found that one-third of adult subjects were seriators and two-thirds were categorizers in a task where either strategy could be employed. Study 1 was a replication of his procedure with children from Grades 1, 3, 5, 7, and 9. While there was weak evidence that some older subjects chose the categorial strategy, there was little evidence for use of the seriation strategy at any age level. In Study 2 we investigated the effects of strategy training with first and sixth graders. Subjects were given either serial, categorical, or no training. Categorical training was highly effective for older subjects, although it had but minor benefits for younger subjects. In contrast, serial training was not differentially effective for older and younger subjects. The data suggested that seriation as a retrieval strategy develops later than categorization, contrary to current theoretical notions. The implications of these developmental trends for adult individual differences in strategy performance were discussed. (Author)