This report details the results of a five-year longitudinal study on the Explainer program at the Exploratorium. Explainers from the summer 1999, fall 1999 and spring 2000 cohorts were interviewed before and after their first semester of work as an Explainer, then followed up with additional interviews three more times at intervals of from one to three years. Additional supplemental data were gathered from a larger set of Explainers via surveys that were administered to these same cohorts before and after their first semester of work, and to a set of Explainer alumni who had been out of the