THREE GROUPS OF DISADVANTAGED CHILDREN WERE ESTABLISHED IN ORDER TO INVESTIGATE THE EFFECT ON ACHIEVEMENT OF PROVIDING SOME CHILDREN WITH A PRESCHOOL PROGRAM AND SOME CHILDREN WITH NO SUCH PROGRAM. AN EXPERIMENTAL GROUP OF HEAD START CHILDREN WERE MATCHED ACCORDING TO SEX, RACE, GENERAL LEVEL OF INTELLIGENCE, AND PARENT'S OCCUPATIONAL LEVEL WITH A CONTROL GROUP OF NON-HEAD START CHILDREN. THE SUBJECTS INVOLVED WERE APPROXIMATELY FOUR TO FIVE YEARS OLD AND ABOUT 200 IN NUMBER. A THIRD NON-MATCHED GROUP OF 41 CHILDREN CONSISTED OF 24 HEAD START SUBJECTS AND 17 NON-HEAD START SUBJECTS. THE TEST RESULTS SHOWED NO SIGNIFICANT DIFFERENCES BETWEEN THE MATCHED GROUPS ON THE VARIABLES OF INCREASE OF INTELLECTUAL ABILITY AND OF LEVEL OF ACHIEVEMENT. ON THE VARIABLE OF SOCIAL ADJUSTMENT, THE HEAD START MATCHED GROUP DID SIGNIFICANTLY BETTER THAN ITS MATCHED NON-HEAD START COUNTERPART ON THE BASIS OF A T-TEST BUT NOT ON THE BASIS OF AN ANALYSIS OF COVARIANCE. THE NON-MATCHED NON-HEAD START GROUP DID SIGNIFICANTLY BETTER ON INCREASE OF INTELLECTUAL ABILITY AND ON LEVEL OF ACHIEVEMENT THAN THE NON-MATCHED HEAD START GROUP, BUT NO OTHER DIFFERENCES WERE FOUND. ALL GROUPS DEMONSTRATED HIGHLY SIGNIFICANT GAINS ON THE VARIABLES ON THE BASIS OF THE WITHIN-GROUP SCORES. (WD)