A study examined the relationship between children's out-of-school activities and their reading achievement. Subjects, 155 fifth graders from a village school and a small city school in Illinois, recorded on daily activity forms how many minutes they spent on a wide range of out-of-school activities. Forms were completed for periods ranging from 8 to 26 weeks. Results showed that of all the ways children spent their time, reading books was the best predictor of several measures of reading achievement, including gains in reading achievement between second and fifth grade. Results also showed, however, that on most days, most children did little or no book reading. Findings suggest that teachers and parents need to give a higher priority to promoting book reading. References, tables and figures are appended. (HTH)