We studied clinical features of 131 patients with juvenile myoclonic epilepsy (JME). The prevalence was 7.7% among the epileptic patients registered. The mean age at onset was 13.37+/-4.93 years and the diagnosis was established at a mean age of 19.53+/-7.85 years. Absence seizures were reported by 27 (20.6%) patients, myoclonic jerks by 131 (100%) and generalized tonic-clonic seizures (GTCS) by 111 (84.7%). The triad of absence seizures, myoclonic jerks and GTCS was noted in 23 (17.5%) patients, 88 (67.2%) had myoclonic jerks and GTCS, 4 (3%) had absence seizures and myoclonic jerks and 16 (12.2%) had only myoclonic jerks. Early onset absences were seen in 21 (16%) patients and the onset was late in 6 (4.6%). Absences antedated other types of seizures in all the patients. Myoclonic jerks were predominantly unilateral or had unilateral onset in 22 (16.8%). In 17 (13%) patients GTCS antedated myoclonic jerks. Myoclonic jerks had characteristic circadian distribution in 112 (85.5%) patients. On awakening GTCS occurred in 87 (78.4%) patients and in 4 (3.6%) patients they were purely nocturnal. Sleep deprivation was the most important precipitating factor (54.2%). Initial electroencephalogram (EEG) showed classical generalized spike or multiple-spike slow-wave paroxysms in 81% of records. Focal EEG abnormalities were noted in 20.6% of records. The most common focal abnormality was voltage asymmetry. A family history of epilepsy was noted in 31 (23.6%) probands. Diagnosis of JME was made in all the cases in the clinic. The factors responsible for delay in diagnosis of the 36 patients seen by neurologists included failure to ask or interpret the history which was otherwise suggestive of myoclonic jerks in all 36 (100%) cases, the type of seizure for which the patients sought medical attention, and misinterpretation of EEGs in 28 patients. Diagnosis of partial epilepsy was made in seven patients. The factors responsible for such diagnoses were, unilateral jerks in one patient, unilateral jerks and absence seizures in three patients and focal EEG abnormalities in three patients.