Acalculia is defined as the inability to mentally manipulate numbers for simple calculations. It may occur in dementia, central nervous system (CNS) neoplasm, and stroke (Bermejo-Velasco and Castillo-Moreno, 2006). Lesions of the left parietal cortex are the principal cause. When acalculia occurs in stroke, it is generally associated with other deficits in speech, sensation, or motor function. We report the case of a 63-year-old male with a 1 day history of isolated acalculia that was found to have a left parietal lobe infarct with several smaller infarcts in the left occipital lobe. The diagnosis of stroke should be considered in all patients experiencing acute difficulty with mathematics, reading, or writing, even in the absence of other deficits.