Seven North American surveys investigation a total of 241,725 hypertensives conducted between 1960-90 were reviewed with respect to their treatment status. In 1960 and 1970 nearly half of hypertensives were unaware of their condition and only 16% were treated and well-controlled. During the time period between 1970-1990 the proportion of the 'unaware' respondents declined to 16%, while the proportion of treated and well controlled patients increased to more than 40%. The proportion of those who are treated but the blood pressure fails to be controlled by the therapy to a satisfactory degree remained essentially unchanged, at around 16%. The proportion of those who are aware of their hypertension but are not treated shows a moderately decreasing trend, still representing 16% of all hypertensives in a recent Canadian survey. Although the handling of hypertension as a public health problem is largely successful, one third of patients still don't receive optimal therapy or is not treated at all.