A comparison was made between scores and grades of college students taking a development and learning course, using either a modified mastery grading system (MMGS) or a modified norm-referenced grading system (MNRGS). Under the MMGS, students could take each unit exam up to three times to meet minimum or higher criteria levels. Under the MNRGS, students took only one test per unit and were assigned grades by comparing their score on the unit (or course average) to the mean of the upper 10% of the distribution of scores (or averages). Although there was improvement in the MMGS group scores and a greater distribution of grades under the MNRGS, repeated testing under the MMGS did not yield significantly higher averages on unit tests or final course averages than those found in the MNRGS group. Four data tables are included. (Author/TJH)