Cytomegalovirus is the most common cause of life-threatening viral infection in HIV-infected patients. This study was done prospectively to investigate the incidence of CMV infection according to the decrease of CD4+ T cell count (CD4+) in Korean AIDS patients. Thirty-nine HIV-infected patients diagnosed before 1994 were followed for regular immunological monitoring. We have used urine shell vial method for the CMV detection from 1994 and have also checked clinical findings. Positive urine culture rate definitely depended on the CD4+ as follows; 45%, 22%, 17%, 11% and 0%, CD4+ >50, 50-100, 100-200, 200-500 and <500, respectively. Except culture positive 2 patients with CD4+ of 200~300/ul, all eight culture positive patients with CD4+ less than 200/ul showed CMV related diseases on or before urine culture. But, we could not get a positive culture for a late AIDS patient with vision loss. With ganciclovir therapy, all culture results were at least negative just after or on late of first 14 days-ganciclovir infusion-course. These data suggest that the incidence of CMV disease in Korean AIDS patients is very high, and early diagnosis and treatment for CMV diseases is required for the prevention of life threatening results.