The acute and chronic effects of hypoglycemia on cognitive and psychomotor performance are reviewed. Studies involving pediatric and adult subjects, both with and without diabetes were evaluated. The preponderance of studies suggest that hypoglycemia can be an unintended yet frequent result of treatment of patients with IDDM. Significant cognitive and psychomotor deficits were reported even with mild episodes of hypoglycemia. Early age of diabetes onset and frequent episodes of hypoglycemia were found to be highly related to significant deficits in intellectual and academic performance. Patients evidencing performance deficits did not always report symptoms of hypoglycemia. Recovery of cognitive functioning lagged restoration of euglycemia but typically returned to baseline levels of performance. Recommendations for improved patient care are provided.