AbstractThis investigation examined the “earlier one starts an intervention, the better” hypothesis for handicapped preschoolers. Posttest performances of handicapped preschoolers on the Bayley Mental Development Index (MDI) and the Bayley Psychomotor Development Index (PDI) were evaluated in relation to the age at which the intervention began, the length of intervention, and Bayley pretest scores. Results indicated that age at start and length of treatment bore little relation to treatment outcomes. However, Bayley pretest scores correlated moderately with posttest scores. Possible explanations are discus