The first multi-institutional survey of the Aicardi syndrome in Japan was performed during 1985 and 1986. Among the 20 collected cases, 9 fulfilled the typical clinical triad; infantile spasms, agenesis of the corpus callosum and chorioretinal lacuna. Three cases had agenesis of corpus callosum and chorioretinal lacuna. Five cases had agenesis of the corpus callosum and infantile spasms. We classified 12 cases with both agenesis of the corpus callosum and a lacuna as typical cases, and the remaining 8 cases as atypical cases. No familial cases were found among either the typical or atypical cases. The presence of the vertebral anomalies or other anomalies in the atypical cases, which were frequently observed in the typical cases, suggested that unknown common processes were affected in both the typical and atypical groups.