OBJECTIVES: To study health status and hospitalization risk among Asian Americans. DESIGN: Cross-sectional analyses and cohort study. SETTING: Comprehensive prepaid health care program in Northern California. PATIENTS: Adult Asian Americans (N=13,592), self-classified at health examinations as 6050 (44.5%) Chinese, 1707 (12.6%) Japanese, 4232 (31.1%) Filipinos, 714 (5.3%) South Asians, and 889 (6.5%) Other Asians. INTERVENTIONS: None except data analysis. OUTCOME MEASURES: With Chinese and Whites (n=72,019) as referents, comparison of symptom composites by logistic regression and hospitalization risk by Cox proportional hazards models. RESULTS: Compared to Chinese, Filipinos, South Asians, and other Asians more frequently reported coronary, respiratory, gastrointestinal, and emotional problems. Chinese and Japanese generally had the lowest hospitalization risk. Compared to Chinese, hospitalization risk was higher (P<.05) among Filipinos for circulatory (men or women), respiratory (men), and digestive (women) conditions (relative risks [RR] range from 1.5 to 1.7) and among South Asian men for cardiovascular conditions (RR=2.2). While Asian groups generally had similar or lower hospitalization risk than Whites, risks were higher for asthma (Filipino and South Asian men, RRs >3.0), peptic ulcer (Chinese men, Filipino men and women, other Asian women [RRs 1.9-5.6]), and coronary disease (South Asian men (RR=2.3) and Filipino women (RR=1.5). CONCLUSIONS: Variations in risk of hospitalization and frequency of reported health problems point out differences in health problems and health needs among subgroups of Asian Americans. This diversity shows the need to study Asian ethnic groups separately.