A study examined the effects of receiving formal reading instruction in kindergarten to 3,959 high school seniors from 24 school districts in 10 states. Over one-third of the subjects attended elementary schools that implemented a carefully developed beginning reading program in their kindergarten class back in 1973. Students from disadvantaged backgrounds were over-represented in the study. Data included measures of the amount of kindergarten reading instruction provided in each classroom in 1973-74; measures of students' family background and educational history variables as high school seniors; and measures of students' reading interests and competencies as high school seniors. A series of comparative analyses examined the relationship between kindergarten reading and subsequent school performance. Results indicated that kindergarten reading experiences were consistently associated with higher reading competency, higher grades in school, better attendance, fewer remedial experiences, and more positive attitudes toward reading. While the results were greatest for students from disadvantaged backgrounds, they held up across subpopulations defined by gender, social class, and ethnic background. Findings indicate strong support for providing formal reading instruction to kindergarten children. (Twenty tables and three figures of data are included; 81 references, a student booklet, a list of study participants, and computer printouts of data are attached.) (RS)