Among 100 infants with infantile spasms studied before treatment, 14 had idiopathic spasms with a favourable outcome. They had a normal development, including reaching for objects before the age of 5 months and moderate regression without loss of eye following. Although it was hysarhythmic, the EEG tracing showed identifiable basic activity and sleep spindles; there was no slow waves focus even after diazepam administration and the spasms were "independent" even during a cluster. This type of infantile spasms seems to be a particular type of non-lesional epilepsy. It contrasts with idiopathic spasms of unfavourable outcome that apparently result from a preexisting and overlooked focal lesion responsible of later cognitive troubles.