Duplicate measurements of BP were recorded at six visits in 32 male urban factory workers found to have raised BP (systolic blood pressure (SBP) greater than or equal to 160 mmHg or diastolic blood pressure (DBP) greater than or equal to 90 mmHg) at the initial visit). A systematic decrease in both SBP and DBP occurred over the first three visits. The BP at visits 4-6 was not significantly different. Most of the decrease in BP occurred between the first and second visit (mean SBP decreased 8.5 mmHg and mean DBP decreased 11.1 mmHg). After 6 visits 66% of subjects could be classified into clear clinical groups (normotensive 53.5%, hypertensive 12.5%) but in 34% the variation in cuff BP precluded classification. In these subjects prolonged observation or home BP monitoring may be required before initiating lifelong treatment.