We present a 46-year-old African-American man with AIDS who was admitted on two different occasions within three weeks for signs and symptoms of meningitis after using trimethoprim/sulfamethoxazole (TMP/SMX). TMP/SMX is primarily used for the treatment of pneumocystis carinii pneumonia prophylaxis in AIDS patients. Drug-induced aseptic meningitis (DIAM) is commonly seen with nonsteroidal anti-inflammatory drugs (NSAIDS), antibiotics (with TMP/SMX being the most frequently implicated), intravenous immunoglobulins and OKT3 antibodies. However, the implication of TMP/SMX inducing aseptic meningitis has been underreported to FDA/MEDWATCH program. This might be due to the fact that it has also been used to treat bacterial meningitis from organisms like Listeria monocytogenes, which is a common pathogen in the elderly and in infants. We reviewed the literature in an attempt to characterize the pattern and predictors of TMP/SMX-induced aseptic meningitis.