Aptitude ratings are quite clearly differentiated from academic course standing and scholastic aptitude test scores, although they appear to be very slightly related to marks in physical training. There is virtually no differentiation among the four sub-categories of aptitude (performance of duty, attitude, bearing and dress, and service desirability). Ratings made by officers and those made by midshipmen agree quite well, except for the 1948 cruise ratings, but officers and midshipmen are not rating in an entirely identical fashion. Midshipmen Composite marks are considerably more stable from one marking period to another than are the officer ratings. There is substantial agreement between aptitude ratings for January 1950 and May 1949 (.81, .67), but considerably less between ratings on the two cruises (.52, .23). Cruise ratings have a good deal in common with ratings made during the academic year, but somewhat different factors seem to be involved in the two situations. The variance of Executive Department marks were found in general to be about 1.5 times as great as the variances of Midshipmen Composite marks.