BACKGROUND Drug-induced aseptic meningitis (DIAM) has been reported as an uncommon adverse reaction to treatment, nonsteroidal anti-inflammatory drugs (NAIDS) stand for most of the published cases. EXEGIS: Our observation reports the first case of a meningeal syndrome with fever, after the administration of ornidazole, with biological aseptic meningitis with lymphocyte prodominance. Spontaneous recovery occurred within a few days and without sequelae. It involved a patient with endocarditis and revealing an intramucous sigmoid adenocarcinoma. The rest of the infection tests was negative. CONCLUSIONS We concluded that we were in the presence of a DIAM, with ornidazole as the most probable implicated agent. This diagnosis is suggested in front of a recurring meningeal syndrome without any other apparent etiology, hence the importance of the questioning of the patient. Pending objective evidence usually provided by rechallenge, an antibiotic therapy is necessary, because it is, above all, a diagnosis of exclusion.