Accidental or intentional isoniazid (INH) overdose is not uncommon. Two patients suffering from pulmonary tuberculosis ingested INH (9 g and 12 g respectively) intentionally following acute personal stress. One patient presented with oliguria and coma whereas seizures were the dominant feature in the second case. Serum levels of INH were high in both cases. Satisfactory clinical recovery followed after the administration of intravenous pyridoxine. Literature on the subject was reviewed and the manifestations and recommendations for the management of acute INH toxicity are highlighted.