Controlled studies have demonstrated that relaxation training can lead to significant in-clinic blood pressure (BP) reductions in patients with essential hypertension. We examined the BP-lowering effect of relaxation training during the working day. Forty-two patients being treated for essential hypertension with diastolic BPs greater than 90 mm Hg were randomized into either a relaxation training program or no treatment. Multiple BP measurements were made during the working hours, using an ambulatory monitoring device, before and after training. Significant work-site differences between groups were evident after treatment both for systolic and diastolic pressures. These results suggest that relaxation therapy leads to a reduction in BP that is evident in the natural environment, providing new evidence that the procedure is a useful adjunct to the treatment of hypertensive patients.