Three basic concerns in measurement were selected, and their importance for the classroom teacher were illustrated. These were test validity, reliability, and problems in measuring achievement gains. Test validity was dependent upon content, type and quality of the questions, adequacy with which the test sampled reading skills, and the care with which the test was administered. Consistency in test reliability was dependent upon the number of samples of a pupil's performance on a task and upon accurate scoring. Measuring gains in pupil achievement was dependent upon correct interpretation and treatment of scores, taking the regression effect and error factor into consideration. References are included. (CL)