In more than two thirds of cases, glutaric aciduria type I begins in the first 3 years of life with an acute encephalopathic crisis with hypotonia or generalized rigidity, neurologic depression, irritability, seizures, and dystonia. The clinical histories were reviewed for 13 glutaric aciduria type I patients (9 male, 4 female; mean age, 8.7 months; range, 3-15 months) with encephalopathic crisis seen at Sant Joan de Déu Hospital, to describe the clinical features and the initial electroencephalographic (EEG) findings. Twelve of the patients (92%) had paroxysmal episodes at onset. Other clinical features included irritability (12/13), neurologic depression (11/13), and hypotonia (7/13). All patients evolved to dystonic tetraparesis. Thirty-five EEGs were recorded in the acute stage and during the first year of follow-up. Spike discharges on EEG were observed in only 2 of the 13 patients, and 8 had slow background activity. No patient developed seizures during follow-up. Seizures may be part of the symptomatology at the onset of glutaric aciduria type I, but most paroxysmal movements appear to be dystonic episodes. This hypothesis is supported by four facts: seizures do not occur after dystonic tetraparesis is noticed, EEG paroxysms are infrequent in the acute stage, antiepileptic drugs are not needed in the long term, and epilepsy is rare in the follow-up.