Objective: There has been increasing interest in the psychiatric literature on research and service delivery focused on first-episode psychosis (FEP), and accurate information on the incidence of FEP is crucial for the development of services targeting patients in the early stages of illness. We sought to obtain a population-based estimate of the incidence of first-episode schizophrenia-spectrum psychosis (SSP) among adolescents and young adults in Montreal. Methods: Population-based administrative data from physician billings, hospitalizations, pharmacies, and public health clinics were used to estimate the incidence of first-episode SSP in Montreal. A 3-year period (2004-2006) was used to identify patients with SSP aged 14 to 25 years. We used a 4- to 6-year clearance period to remove patients with a history of any psychotic disorder or prescription for an antipsychotic. Results: We identified 456 patients with SSP, yielding a standardized annual incidence of 82.9 per 100 000 for males (95% CI 73.7 to 92.1), and 32.2 per 100 000 for females (95% CI 26.7 to 37.8). Using ecologic indicators of material and social deprivation, we found a higher-incidence proportion of SSP among people living in the most deprived areas, relative to people living in the least deprived areas. Conclusions: Clinical samples obtained from psychiatric services are unlikely to capture all treatment-seeking patients, and epidemiologic surveys have resource-intensive constraints, making this approach challenging for rare forms of psychopathology; therefore, population-based administrative data may be a useful tool for studying the frequency of psychotic disorders.