This bulletin reviews selected research on the relationship of increased instructional time to student achievement. Different ways of increasing time are discussed, including lengthening the school year and the school day, reallocating time within the day to allow more time for instruction, improving teachers' management skills, and increasing homework assignments. The research reviewed generally supports the conclusion that increased instructional time has modest beneficial effects on learning. However, the relationship between time and achievement is not strong, and policymakers should not expect large gains to result from increasing the amount of instructional time in the school day or year. The research is also inconclusive on the most effective and practical ways to increase time. Thirty-six references are included. (TE)