The influence of beta blockers on Type A behavior pattern and cardiovascular reactivity was tested. Nineteen white, male hypertensive patients were divided at random into two therapeutic groups (100 mg atenolol versus 50 mg hydrochlorothiazide + 5 mg amiloride (control group) ). For each patient, the German version of the structured interview was performed before therapy and at a minimum of 4 weeks after normalization of clinical resting casual blood pressure (BP). Prior to therapy, there were no differences in age, BP at rest, cardiovascular reactivity, and Type A between the two groups. After therapy, the patients treated with beta blockers changed Type A characteristics toward Type B, regardless where they started on the Type A scale, and beta blockers attenuated cardiovascular reactivity. In this study, Type A (hypertensive patients) was not associated with greater cardiovascular reactivity.