Part 1 of this study investigated possible causes of the observed decline in correlations between SAT scores and freshman grade-point average (FGPA). Working with a database of 38 colleges, the study found that the comparability of course grades received by entering freshmen declined in the 1980s. Three new measures of grade comparability-variety of courses taken, variation in average student aptitude among courses, and appropriateness of average course grade in relation to student aptitude level-proved to be excellent indicators of both the level of and the change in SAT validity for predicting FGPA. Using course grade as a criterion instead of FGPA reduced the decline in both SAT and high school GPA (HSGPA) validity for predicting course grades by 40 percent. Contrary to the assumption that high school record (HSR) is a better predictor than the SAT, compared with HSR the SAT had higher or equal average validities for predicting course grades in almost all categories of courses. Part 2 examined course selection, grading patterns, grade comparability, SAT predictive effectiveness and mean over- and underprediction across different courses for groups based on gender, English as best or not best language, and ethnicity. All results were analyzed by college selectivity level and size. The following are appended: (1) Colleges Participating in the Study; and (2) Course Categories.