Febrile seizures are a common pediatric problem, yet there is a great deal of disagreement about the appropriate diagnostic evaluation of a child with this disorder. We reviewed the routine diagnostic tests performed on 100 consecutive children admitted with their first "simple" febrile seizure. The studies performed included lumbar puncture, measurement of blood glucose, serum calcium, serum electrolytes, and BUN levels, blood cell count, urinalysis, skull roentgenograms, and EEG. Though resulting in a significant expense, these routine investigations proved to be of little diagnostic value. Based on this experience and a review of the current literature, we concluded that diagnostic procedures should be performed only when specifically called for by the patient's condition or medical history.