A comparison of blood pressure (BP), smoking, alcohol consumption and obesity between whites and blacks of Caribbean origin aged 17-70 was undertaken in a general practice in North West London. Mean systolic and diastolic blood pressures (DBP) showed no consistent overall differences between the two ethnic groups, though DBP rose significantly more with age in black males than white males. Somewhat higher proportions of the black patients were receiving anti-hyper-tensive treatment compared with the whites, the difference was statistically significant in the case of males (P less than 0.02). This observation did not appear to be due to more effective detection of hypertension amongst black males. Overall, fewer than one-third of black females were current cigarette smokers compared with around one-half of white females (P less than 0.001). Amongst males, however, the proportions of never, ex and current smokers were similar in the two ethnic groups. Young black patients of both sexes were more likely to smoke than older blacks. Blacks who smoked tended to smoke fewer cigarettes than white smokers. Eleven of 190 (5.8%) black males had consumed 35 units or more of alcohol within the last week compared with 87 of 452 (19.2%) of white males, (P less than .001). Amongst females the differences were smaller, 5 of 227 (2.2%) of black females had consumed 21 units or more in the last week compared with 23 of 490 (4.7%) of white females (NS).(ABSTRACT TRUNCATED AT 250 WORDS)