Data from the 1975-1976 National Ambulatory Medical Care Survey conducted by the National Center for Health Statistics were examined retrospectively to determine the extent to which blood pressure was measured during visits to office-based physicians in the conterminous United States. Blood pressure was more often measured for females (especially black) than for males although males (especially black) in certain age groups had a higher prevalence of hypertension and comprised the higher proportion of undiagnosed hypertensives. Blood pressure measurement increased with age, but was rarely measured for those under 15 years of age. Blood pressure was measured about 79 per cent of the time when hypertension was present but only 30 per cent of the time when hypertension was absent. When diseases shown to be frequently concomitant with hypertension were diagnosed in the absence of hypertension, blood pressure checks ranged from 24 per cent of visits diagnosed neuroses to 66 per cent diagnosed obesity. Blood pressure was measured during about 12 per cent of visits for diseases of the nervous system and sense organs as well as diseases of the skin and subcutaneous tissue; 24 per cent of visits for infective and parasitic diseases, diseases of the respiratory system, and mental disorders. Blood pressure was measured most often when diagnoses were in the categories of diseases of the circulatory system and endocrine, nutritional, and metabolic diseases. Opportunities for blood pressure measurement during routine visits did not appear to be fully utilized, nor did some specialists take frequent blood pressure measurements. (Am. J. Public Health 69:19-24, 1979.)