We studied 39 AIDS patients from 1989 to 1996, with previous history of herpes zoster. Twelve of them received acyclovir (ACV) secondary prophylaxis. There were 31 males and 8 females, mean age 33.9 years (19-60) during first herpes zoster. Transmission was sexual in 71.8%. Among these 39 patients, 78 herpes zoster episodes occurred. Median CD4 lymphocytes was 18/mm3 (0-232) among the 12 patients with ACV prophylaxis. Mean posology of ACV was 2,400 mg (1,600-4,000) per day, during mean 10 months (median 4 months). ACV prophylaxis was used because of high frequence of herpes zoster (more than 4) (4 cases), neurologic complications in 4 cases (1 myelitis, 1 myeloradiculitis, 1 vascularitis and 1 meningo-encephalitis), disseminated herpes zoster in 4 cases and one hyperalgic zoster. Ten from these 12 patients occurred no zoster recurrence. Among patients without prophylaxis, zoster recurrences were more frequent at 12 months (68% versus 22% among patients with prophylaxis). This prophylaxis seems to be interesting, particularly in deep immunocompromised patients (CD4 < 50/mm3) with serious herpes zoster or frequent recurrences (more than 4). However, since protease inhibitors treatments, zoster incidence is decreasing in HIV+ patients. This prophylaxis will probably be less usefull than before.