How well one retains new information depends on how actively it is processed during learning. Active attempts to retrieve information from memory result in more learning than passive observation of the same information (the generation effect). Here, we present evidence for the generation effect in monkeys. Subjects were trained to respond to five-item lists of photographs in a particular order. On some lists, they could request "hints" to guide their behavior; on others, they had to generate the correct order from memory. Training with hints resulted in high levels of initial performance, but accuracy dropped precipitously when the hints were removed on the criterion test. Training without hints led to relatively poor initial performance, but accuracy increased steadily and remained high on the criterion test.