Fifty-six consecutive symptomatic patients with AIDS referred for gallium scintigraphy were prospectively studied with chest high-resolution computed tomography (HRCT). Results of gallium and HRCT were correlated with findings of bronchoscopy or clinical follow-up for 1 month from time of discharge. Twenty-two patients were eventually diagnosed with at least one of the following: Pneumocystis carinii, cytomegalovirus, Mycobacterium avium complex, bacteria, Kaposi's sarcoma, or lymphocytic interstitial pneumonitis. HRCT was more sensitive (82%) and more specific (91%) than gallium (59% and 75%, respectively). HRCT yielded higher positive predictive values (86%) and negative predictive values (88%) than did gallium (62% and 73%, respectively). HRCT was more helpful in guiding the method of biopsy and directing the brochoscopist to the diseased lung segment that would maximize diagnostic yield.