Gender differences in achievement test performance at the college level were studied as part of the initial analysis of the recently developed Collegiate Assessment of Academic Proficiency (CAAP)--an achievement test battery for use in higher education. The CAAP was pilot tested in fall 1988 and includes a measure of writing proficiency and four objective tests: (1) reading; (2) writing skills; (3) mathematics; and (4) critical thinking. Random samples of 1,000 males and 1,000 females were drawn for each objective test from students from about 100 post-secondary institutions. The students tested were primarily incoming college freshmen. The total number of examinees (n=1,490) was included in the writing analysis. The means, standard deviations, t-statistics, and effect sizes for each test indicated that females tended to perform better than males on the multiple-choice writing skills test and on the essay test. Males tended to outperform females on the mathematics test. There were no overall performance differences between males and females on the reading and critical thinking tests, but there were differences associated with individual passages. Effect sizes for performance differences were generally small, but were in keeping with results found for other tests and examinee populations. Two data tables are provided. (SLD)