In a 37-year-old patient HIV infection was diagnosed in June 1986. Eight years later the patient complained of increasing shortness of breath and occasional syncopes on exertion. He developed peripheral oedema and ascites. Echocardiography revealed severe pulmonary hypertension. Right ventricular systolic pressure (RVSP) was 77 mm Hg. There was no evidence of left ventricular dysfunction, valvular heart disease, thromboembolic disease or obstructive or restrictive lung disease, nor were there other known causes or risk factors of pulmonary hypertension. HIV-associated pulmonary arterial hypertension was diagnosed. Oral anticoagulation and zidovudine were begun, but RVSP rose to 96 mm Hg. After the introduction of lamivudine, and later stavudine and nelfinavir, HIV-RNA copies decreased from 133 400 to below 50 copies per mL. Six years after the diagnosis of HIV-associated pulmonary arterial hypertension RVSP had continually fallen to 49 mm Hg and the grossly enlarged right heart dimensions had nearly normalised without vasodilator treatment. The patient remains in excellent health and his sole complaint is of mild dyspnoea on exertion.