In a preliminary random study of 1 000 rural Zulus the overall prevalence of primary hypertension was 10,5% (females 10,75%, males 10%). Women between the ages of 31 and 40 years had a higher prevalence than men. The mean arterial pressure in relation to age and sex was not as high as in urban Zulus. The urban Zulus had a more definite rise in mean arterial pressure after 30 years of age. A diastolic blood pressure greater than or equal to 95 mmHg was present in 8,1% of the subjects and 2,3% had a diastolic blood pressure of greater than or equal to 105 mmHg. This study suggests that hypertension is not a major health problem in rural Zulus and that large-scale case-finding and intervention programmes should be confined to the urban Black population of South Africa.