The distribution of arterial blood pressure (BP) values of 1499 adult inhabitants of four Newfoundland communities was surveyed. Mean age- and sex-adjusted BP scores were found to be higher in each of three fishing villages than in the logging and mining community, Badger, in the central part of the province. It is postulated that the observed differences may be caused by environmental factors. The prevalence of individuals with probable essential hypertension (diastolic BP > 100 mm. Hg) in individuals over 50 years of age was found to be three times higher in the island community, Fogo, than in Badger. In both communities less than one third of those with probable hypertensive disease had received treatment.