The aim of this study was to evaluate the presence of "type A" behaviour and possible psychological distress in 373 hypertensive patients. One-hundred and ninety-five males, 56.2 +/- 6.2 years old and one-hundred and seventy-eight females, 57.1 +/- 6.2 years old, coming from the IPPPSH and still under double-blind treatment with or without a beta-blocker (oxprenolol 160 mg SR), were studied by means of the Jenkins Activity Survey form C and several tests from the Cognitive Behavioural Assessment Battery (CBA-2.0). Seventy-four point eight percent of the patients showed a "type A" pattern, and 25.5% were in the extreme predictive interval for coronary heart disease according to WCGS. "Type A" pattern was not influenced by variables such as age, sex, education, job or previous pharmacological treatment. The patients studied did not show any particular psychological distress at the psychometric evaluation. However, special social and cultural characteristics and different therapies influenced some symptoms, such as anxiety, depression and somatic lamentation. According to this study: "type A" behaviour seems to be a steady feature of the hypertensive patient; furthermore, it seems to be due to a "biological imprinting" which can be considered a cause of hypertension; psychological distress depends on a particular set of environmental stimuli. In the first case an accurate prevention is needed while, in the second case adequate pharmacological and/or psychological therapies are needed.