A study was conducted to measure the effect and compare the results of developmental reading instruction for college students as prescribed from the specific results of a diagnostic reading test and a general, more traditionally used, survey reading test. The sample consisted of 226 students enrolled in different sections of a reading course required at the University of South Carolina for students with low Stanford Achievement Test scores. All students received two hours per week of classroom instruction. Experimental and control treatments were provided by graduate assistants for one hour of lab time each week. Individual prescriptions for lab instruction were written for the experimental students based on information from the subtests of the Stanford Diagnostic Reading Test only. Only the information from the subtests of the survey instrument, the Nelson-Denny Reading Test, was used in writing prescriptions for the control students. The gain in reading was measured by the pretest and posttest differences on both tests. There was a statistically significant difference in the means of the gain scores between the experimental students and the control group on many of the subskills on the Stanford Diagnostic Reading Test. However, the gains on the Nelson-Denny Reading Test did not reflect evidence of a significant difference. (MKM)