The mortality and morbidity from coronary heart disease (CHD) is higher in people of South Asian origin than in whites, but is significantly lower in the black (Afro-Caribbean origin) community in the United Kingdom. To investigate whether this may be related to differences in fatty food intake, we performed a questionnaire survey of the weekly food purchasing habits and preparation methods in white, black (Caribbean) and Asian households in Birmingham. We interviewed 224 housewives from three ethnic groups (84 white, 76 black/Afro-Caribbean and 72 Asian). The highest quantity of fat in foods purchased per week was found in the Asian population (median 1409 g/week per person, interquartile range (IQR) 850-1952), which was significantly greater than black subjects, who had the lowest quantity of fat in foods purchased (1012 g/week per person, IQR 835-1388) (Mann-Whitney test:median differences 300.5, 95% C.I. 23.3-600.4, P = 0.029). The median quantity of fat in foods purchased by the white households was intermediate, at 1186 g/week per person (IQR 861-1711). There was a higher quantity of fat in foods purchased in the lower social classes (IV and V) in both the white and Asian populations. Butter, egg and milk consumption was significantly greater in Asians; with ghee consumption almost exclusive amongst this group (98%). Amongst whites and blacks, the commonest food preparation methods were grilling, boiling or poaching; whilst amongst Asians, frying was more common (chi 2 = 81.25, d.f. = 4, P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)