The language development component of Columbus, Ohio's All Day Kindergarten Program (ADKP) was evaluated. The ADKP was instituted in Columbus' public schools in January, 1972, to provide a full day of instruction for underachieving kindergarten pupils. In the 1988-89 school year, 18 teachers served in 18 elementary schools that were eligible for Chapter 1. Each provided daily instruction for two groups of 15 pupils each for about 13 hours a week. For evaluation purposes, the ADKP provided 114 days of instruction. Pupils included in the final pretest-posttest analysis attended at least 91.2 of the 114 days. Data were collected in five areas: (1) pupil census; (2) standardized achievement test scores; (3) teacher census; (4) parent involvement; and (5) inservice evaluation. The overall Normal Curve Equivalent (NCE) gain for the program averaged 17.6 NCE points for the 5.7 month treatment, or 3.1 NCE points for each month of treatment. Based on evaluation results, it was strongly recommended that the ADKP be continued in the 1989-90 school year. Results are discussed and steps for improving program effectiveness are specified. Pupil and teacher census forms, parent involvement survey forms, and general and orientation inservice evaluation forms are appended. (RH)