We analyse the characteristics of patients diagnosed with HIV infection in the highly active antiretroviral therapy era in the southeast of Spain. Data were collected on 470 HIV patients diagnosed between January 1997 and December 2002. The number of cases fell over recent years and HIV transmission was sexual in 70.5%. The mean CD4 lymphocyte count was 302.1 x 10(6)/L and the mean viral load 4.70 log(10). Diagnosis of HIV coincided with an AIDS-defining opportunistic illness in 30.6% of patients and a late diagnosis (CD4 < 200 x 10(6)/L) was made in 48.3% of patients. A late diagnosis was related to male gender (OR 2.50; 95% CI 1.20-5.12; P < 0.001) and AIDS case (OR 18.80; 95% CI 10.50-33.80; P < 0.00001). These results suggest that there has been a progressive reduction in new cases of HIV-infected patients, with the main route of transmission being sexual and that the diagnosis was late in almost half the patients.