Eighty-five fourth- and eighth-grade learning disabled students whose individualized education plans specified untimed achievement testing were tested with the Reading Comprehension subtest of the Iowa Tests of Basic Skills, either according to the publisher's 40-minute time limit or with an extended time limit of 2 hours, 30 minutes. Results were compared with those from a parallel form of the test administered 8 months earlier. Measures included grade-equivalent and normal curve equivalent scores, completion rates, amount of time needed to complete the test, and KR-20 reliabilities based on students in each cell. All but one of the fourth graders in the extended time group finished the test in the publisher's time limit. Twenty-two of the 26 eighth graders in the unlimited time group took longer than the publisher's limit. Despite some methodological problems centering around student motivation and attitudes toward testing, the study suggested that the test may be more reliable when administered without time limits, and students' merely knowing that unlimited time is available may yield higher scores, even if no additional time is actually used. (Contains 5 tables and 10 references.) (Author/SLD)