This study has examined the relationships of health-related behaviours to sociodemographic factors with special emphasis on ethnicity in Hawaii. Behavioural variables investigated were non-use of car seat belts, overweight, physical inactivity, smoking, heavier alcohol use, and driving while intoxicated. Sociodemographic factors considered were ethnicity, island, sex, age, education, employment status, marital status, and household income. Major ethnic groups studied were Caucasians, Hawaiians including part-Hawaiians, Chinese, Filipinos, and Japanese. The relationships of ethnic factors with the behavioural characteristics were studied by logistic regression after fitting significant non-ethnic sociodemographic variables. Multiple risk behaviour was investigated by canonical correlation analysis. Different behavioural factors were found to be associated with different sets of non-ethnic socioeconomic variables. There were significant ethnic differences in individual at-risk behaviours except for driving while intoxicated. Overweight was most prevalent among Hawaiians followed by Caucasians. Caucasians and Hawaiians were at higher risk for non-use of seat belts, cigarette smoking, and heavier alcohol use compared to Chinese, Filipinos, and Japanese. Orientals were physically less active than Caucasians and Hawaiians. Implications of the observed ethnic differences are discussed.