This paper presents data on the reporting of illnesses, disability due to illnesses and the decision to seek medical attention for illnesses among a representative sample of Mexican-Americans, Black-Americans and White-Americans in Los Angeles. Few differences were observed among these groups with respect to the reporting of illnesses, disability due to illnesses or in the frequency with which illnesses were brought to medical attention. Hierarchical stepwise multiple regressions were run for each of these variables within each of these subgroups. Some differences were found among these groups in the variables that predicted illness reporting, disability and the use of physician services for illnesses. These differences indicate that ethnicity affects health behaviour through its interaction with other variables. Speculations are offered regarding the meaning and historical sources of the differences observed.