OBJECTIVES: Hospital admission is a common and costly event in schizophrenia. An analysis of phase 1/1A CATIE clinical trial data assessed various patient socio-demographic and clinical characteristics in relation to risk of psychiatric hospital admission. METHODS: We followed 1460 study participants from baseline until first schizophrenia-related hospital admission, study medication discontinuation, or 18 months. Stepwise Cox regression models assessed the adjusted hazard ratio (AHR) of hospital admission by baseline patient socio-demographic and clinical characteristics. RESULTS: In 869 person-years of follow-up, 203 patients were hospitalized. The adjusted hazards of hospital admission were not significantly related to patient socio-demographic characteristics. Increased risk of admission was linked to early age (<17 years) of first antipsychotic treatment (AHR: 2.09; 95%CI: 1.45-3.02), psychiatric hospital admission in past year (AHR: 2.92; 95%CI: 2.18-3.90), and DSM-IV alcohol (AHR: 1.55; 95%CI: 1.15-2.08) and drug (AHR: 1.50; 95%CI: 1.13-2.00) use disorders in the past 5 years. Severe (5-7) as compared with mild (1-3) baseline global clinical severity (AHR: 1.51; 95%CI: 1.03-2.23) (CGI-I), high (>20) as compared with low (7-15) positive symptoms (AHR: 1.53; 95%CI: 1.08-2.16) (PANSS-positive subscale), and low (0-2.2) as compared with high (>3.1) social function (AHR: 1.47; 95%CI: 1.04-2.08) (Heinrichs-Carpenter QLI) were related to significantly increased risk of hospital admission. As compared with olanzapine treatment assignment, quetiapine (AHR: 2.12; 95%CI: 1.37-3.27), perphenazine (AHR: 1.64; 95%CI: 1.02-2.65), and ziprasidone (AHR: 2.67; 95%CI: 1.62-4.39), though not risperidone (AHR: 1.40; 95%CI: 0.89-2.21), were also associated with increased hospital admission risk. Self-rated physical health (SF-12 PCS) and drug attitudes (DAI) were not significantly related to risk. CONCLUSIONS: In the treatment of schizophrenia, efforts to lower hospital admission risk should focus on patients with early onset disorders, recent inpatient admissions, severe positive symptoms, high global clinical severity, poor social function, and comorbid substance use disorders and should select an appropriate antipsychotic medication.