Since its initial description by Mollaret in 1944, the etiology of the chronic aseptic meningitis has remained unknown. This rare disease may cause diagnostic problems if bacterial or viral causes are suspected. A different form of aseptic meningitis may be seen following a variety of drug treatments, especially with non-steroidal anti-rheumatic drugs: In many reports since 1978, meningitic attacks following administration of ibuprofen have been reported. We describe two cases of Mollaret-Meningitis with certain specialities: one case shows clear encephalitic involvement with aphasia in all six attacks. In the other case, five meningitic attacks appeared spontaneously, while two were drug-induced: the first attack was seen after a lumbar myelography with lopamidol and one attack appeared two hours after oral administration of 400 mg ibuprofen. It is suggested that Mollaret-Meningitis is a special form of a drug-induced allergic reaction, the provoking agent of which remains unknown.