We report seven families and two sporadic cases in which benign infantile convulsions and paroxysmal kinesigenic choreoathetosis were co-segregated. Clinical investigations included physical and neurological examinations, blood electrolyte values, interictal and ictal electroencephalograms, and computed tomography or magnetic resonance imaging of the brain. The family pedigree was confirmed and the clinical history of the relatives was obtained. Seventeen individuals developed infantile convulsions followed by paroxysmal dyskinesias during childhood or adolescence. Six had only infantile convulsions, and two had only paroxysmal dyskinesias. The seizures never persisted into childhood or recurred in adulthood. The seizure type was a complex partial seizure, with or without secondary generalization, in nine of 14 patients. Paroxysmal dyskinesias, a subgroup of paroxysmal kinesigenic choreoathetosis, occurred for less than 5 min. The attacks of dyskinesias began at age 5-12 years in most patients, and tended to remit in adulthood. The mode of inheritance was apparently autosomal dominant in four of the families (17 affected individuals), who were diagnosed with ICCA syndrome (infantile convulsions and paroxysmal choreoathetosis). However, the condition occurred only among siblings in three families (six patients), and sporadically in two patients, suggesting genetic heterogeneity in this distinct co-segregation.