Scores on the 20 aptitude and achievement tests given in July 1948 have been correlated with each other and with first and second term grades at the Naval Postgraduate School. The following tests correlated higher than .40 with the criterion of Quality-Point Ratio for both of the terms: (1) Engineering Achievement Test in Mathematics, (2) Physics SA, (3) the Graduate Record Examination Advanced Test in Engineering, (4) Reading Comprehension, (5) Mathematics WSA2, and (6) Mathematics WIM3. Several other tests showed significant but lesser degrees of validity for predicting the Q.P.R. or one or more course grades. The technique of multiple correlation was also used, and showed that mathematics and engineering were the two areas which contributed most heavily to the prediction of grades in the first two terms. Item analyses of the mathematics, engineering and physics tests have been carried out as an aid to further test development. Results for the first two terms have been very encouraging and indicate that initial efforts to predict academic success at the Naval Post- graduate School have been quite fruitful.