The purpose of this study was to determine whether any differences in academic achievement existed between full-day and half-day kindergarten students at the end of their kindergarten and first-grade school years. Two public schools considered comparable in size, philosophy, and socioeconomic levels of a large school district in Texas participated in the study. One of the schools provided a full-day kindergarten program; the other school provided a half-day kindergarten program. Kindergarten students from each of the two schools were match-paired according to birthday and sex. The total sample size was fifty students. All students were tested in December, 1985, with the Metropolitan Achievement Test. Preprimer Level, and in May, 1986, the end of the kindergarten year, with the Primer Level of the Metropolitan Achievement Test. The Metropolitan Achievement Test. Primary I Level, was additionally administered to the subjects in April, 1987, at the end of their first-grade school year. During each testing period, the subjects were administered the Reading, Language, and Math subtests of the Metropolitan Achievement Test. The following supplemental data also were gathered on the students: The Metropolitan Readiness Test II scores and the TEAMS test scores. The data obtained from the testing batteries were statistically analyzed using the .05 level of significance to test each hypothesis. In analyzing the data of all of the academic achievement testing batteries, statistical conclusions revealed that there was no significant difference in the mean scores of children (boys or girls) attending the fullday kindergarten program and children attending the half-day kindergarten program in academic achievement at the end of the kindergarten year or at the end of the first-grade year. It is recommended that continued studies be conducted to investigate the academic achievement of students attending full-day and half-day kindergarten programs. It is also recommended that other variables rather than academic achievement be studied to determine their effects on full-day and half-day kindergarten students.