A quasi-experimental study explored the ways in which the full-day kindergarten program is beneficial and/or detrimental to students compared to the half-day and/or extended-day program. The sample consisted of six full-day schools matched with half-day schools on geographic location, school size, student norm-referenced data, and socioeconomic status of patrons. Data were collected by means of classroom observations; video- and audiotaped interviews of students, teachers, and parents; report cards of all students included in the sample; survey questionnaires administered to parents and teachers; and a norm-referenced achievement test administered to all students. The findings revealed the following: (1) greater utilization of small group activities by the full-day programs; (2) no significant difference in the amount of fatigue experienced by full-day and half-day students; (3) greater number of social interactions was experienced by full-day students; (4) full-day students outperformed half-day students on the majority of the Language Arts criteria and a few of the criteria used to measure mathematics skills; (5) full-day students outperformed half-day students on every criterion measured by norm-referenced achievement test; (6) overall satisfaction was higher for parents of children attending full-day and extended day programs (they believed that their children had a better chance for success in first grade over the half-day students); and (7) school attendance of full-day students was more regular than for other students. (BA)