A study ascertained the degree of relationships between scores on each of various reading subskills and overall reading success. Reading subskills were measured by locally developed reading skills tests. Overall reading success was measured by the reading subtest of the Iowa Tests of Basic Skills (ITBS). In each of three southern Indiana school districts, task forces of teachers had designed and constructed a series of reading skills for each of several grade levels. In school 1, 501 students were tested in grades 1-6; 189 students were tested in grades 1-6, 8, and 10 in school 2; and in the third school, 89 students were tested in grades 3, 5, and 8. The tests had been field tested and revised. All tests had reliabilities above 0.91. Tests averaged 20 skills per grade level. There were 6 test items per skill for the first group tested and 10 items per skill for the second and third groups tested. Tests were administered to a total of 758 students at the three sites. Results of the subskills tests were compared to the scores of the ITBS. Multiple regression analysis was performed to determine the amount of relationship between scores on local skills tests and overall reading effectiveness. Results indicated that: (1) phonics instruction in the primary grades did not correlate with reading comprehension; and (2) the use of context clues to determine word meaning was highly related to overall reading effectiveness. (RS)