In recent years there has been a marked improvement in the level of hypertension control nationally in both blacks and whites. Information is still lacking, however, on the level of hypertension control in Mexican Americans. The authors carried out a cardiovascular risk factor survey on a random sample of Mexican Americans living in two low income census tracts in Laredo, Texas. The percentages of hypertensive women who had been previously diagnosed, were under treatment, and were "under control" compared favorably with national figures for blacks and whites. Corresponding percentages for men indicated that their level of diagnosis, treatment and "control" still lagged behind the national figures. The prevalence of hypertension in Laredo Project participants was intermediate between those observed in national studies for blacks and whites. This finding did not clearly emerge when comparisons were based on either blood pressure distributions or prevalence of elevated diastolic pressures. These results indicate that, because of the increasing number of "controlled" hypertensives in the population, comparisons between populations and across time can no longer be based exclusively on blood pressure measurements, but must include cases of "controlled" hypertension.