Two experiments examined the development of recollection (recalling qualitative details about an event) and familiarity (recognizing the event) using the dual-process signal detection model. In Experiment 1 (n = 117; ages 6, 8, 10, 14, and 18 years), recollection improved from childhood to adolescence after semantic encoding but not after perceptual encoding and familiarity improved from ages 6 to 8 regardless of encoding condition. In Experiment 2 (n = 56; ages 6, 8, and 10 years), long duration compared to short duration of semantic encoding increased familiarity but not recollection. Age-related differences replicated those of Experiment 1, except no age difference in familiarity was found with long study duration. Overall, recollection and familiarity showed distinct developmental and functional characteristics. The dual-process signal detection model proved promising for developmental investigations.