Human immunodeficiency virus-infected (HIV) patients frequently present left ventricular dysfunction. Its etiology is not elucidated but zidovudine has been postulated as a possible cause factor. This study is an attempt to clarify this issue by evaluating the effect of zidovudine therapy on left ventricular function in these patients. We prospectively studied by echocardiographic examination 11 consecutive HIV-infected patients who were assigned for zidovudine therapy. We excluded patients that had a history or a physical examination suggestive of ischemic, rheumatic, congenital, or hypertensive heart disease. Patients with diabetes mellitus, excessive ethanol intake and patients on potentially cardiodepressant drugs were also excluded. Echocardiographic examination was performed immediately before the initiation of zidovudine therapy and 1 and 3 months later. Left ventricular diameters, mass and fractional shortening showed no significant difference from baseline, at 1 or 3 months after the initiation of zidovudine therapy. Our results suggest that zidovudine therapy has no effect on left ventricular diameters, mass or fractional shortening during a short term.