This study compared the performance of kindergarten children who had participated in a full-year Head Start program (FYHS) with that of children who had attended summer Head Start (SHS). FYHS subjects at each of two elementary schools were selected at random from eligible applicants. SHS comparison groups were made up primarily of children from the same initial lists of subjects. On a group of measures administered about 8 months after completion of the Head Start programs, no significant differences were shown between FHYS and SHS children, or between the two elementary school groups. SHS children, however, earned significantly higher IQ scores at the end of kindergarten than they had early in Head Start, and FYHS children showed a significant progressive increase in IQ over a 2-year period covering Head Start and kindergarten. This continuous increase in IQ is noteworthy, since previous studies have found a leveling-off effect following an initial gain in Head Start. It is recommended that follow-up studies concentrate on the long-range effects of FYHS programs with defined curricula focused on cognitive development. (Author/NH)