We present the case of a 66-year-old male patient, hypertensive, with diffuse gastric adenocarcinoma stage IV and malignant tumor of right orbit. The patient consulted for loss of consciousness and incoherent language. Physical examination revealed meningeal signs. Lumbar puncture showed elevated opening pressure, pleocytosis, hypoglycaemia, hyperproteinorrachia, high lactate, with negative microbiological examination. These clinical data and CSF analysis initially determined acute meningitis. However, the neurological service proposed as a diagnostic impression meningeal carcinomatosis, which required three lumbar punctures to confirm it. Meningeal carcinomatosis is a differential diagnosis that must be considered in a patient with tumoral pathology and meningeal signs. Clinical suspicion, cytochemical findings, and cytology by CSF cyto-centrifuge are important.