As the number of studies related to the early identification of and intervention in the schizophrenia prodrome continues to grow, it becomes increasingly critical to develop methods to diagnose this new clinical entity with validity. Furthermore, given the low incidence of patients and the need for multisite collaboration, diagnostic and symptom severity reliability is also crucial. This article provides further data on these psychometric parameters for the prodromal assessment instruments developed by the Prevention through Risk Identification, Management, and Education (PRIME) prodromal research team at Yale University: the Structured Interview for Prodromal Syndromes and the Scale of Prodromal Symptoms. It also presents data suggesting that excellent interrater reliability can be established for diagnosis in a day-and-a-half-long training workshop.