Data on blood pressure was extracted from the findings of a 6-week double-blind study that was carried out to evaluate the efficacy and safety of prescribing tranylcypromine (TCP) singly and in combination with amitriptyline (AMI). The effect of TCP on blood pressure was one of the methods used to evaluate its safety. Target daily doses of medication for the final 2 weeks of the study were: TCP 30 mg, AMI 150 mg, or the two in combination. Because of side effects, mean daily doses actually achieved were lower: single TCP 18.5 mg; single AMI 114.3 mg; combined TCP/AMI: TCP 19.7 mg, AMI 108.7 mg. When TCP alone was prescribed, a significant fall in diastolic blood pressure in the standing position was noted and orthostatic hypotension was more frequently observed. Dizziness was complained of on at least one occasion in over three quarters of patients on TCP/AMI. No correlation between blood pressure effects and dizziness was detected and there were no other troublesome side effects from this antidepressant combination. The study concluded that although TCP's overall effect on mean blood pressure readings when prescribed alone or in combination was small, its orthostatic effect is noteworthy and should be borne in mind by the prescribing clinician.