The authors report on the factor which interferes on follow-up of children affected by infantile spasm. On the basis of their series and on the data of literature the factor more indicative for the clinical evolution are: type and dosage of treatment, onset early or delayed, and the aetiology. While for the first two factors the opinion of the expert are remarkable discordant, there is a general agreement that the evolution of infantile spasm is mainly based on the causes determining such kind of epilepsy.