We report the case of a 44-year-old right-handed man with severe acalculia and 4 normal age-matched controls. The acalculia patient had magnetic resonance findings of a wedge shaped defect in the left posterior temporal-parietal cortex, involving the angular gyrus, and a lacunar infarct of the right thalamus. Functional magnetic resonance exams were performed utilizing four tasks consisting of serial subtracting by sevens, basic calculation, complex calculation, and abstract calculation. Both patient and controls showed specific task-related activation with some differences that may indicate brain plasticity, even though no significant recovery in calculations abilities was observed in the patient.