This study was designed to determine the accuracy with which high school students estimate their cognitive abilities as measured by the Armed Services Vocational Aptitude Battery (ASVAB). In addition, the study was designed to determine whether participation in vocational counseling activities through the ASVAB program or through Florida CHOICES/View is related to scores on a measure of career development. Subjects were 1,105 10th-, 11th-, and 12th-graders from 10 high schools in Florida. They were participants in a larger study involving 9,000 students. Major instruments used included the ASVAB and the Career Development Inventory (CDI). The CDI contains a slightly revised 52-item version of the Career Exploration Survey and other items dealing with students' career intentions and activities. The CDI was administered in the fall of 1986 and in the late spring of 1987. The ASVAB was administered between the two CDI administrations. Results indicate that: (1) students are not good estimators of their abilities; (2) males and females have different estimation patterns, with females showing more variability in inaccurate estimation; (3) accuracy of estimation is not related to ability level; and (4) underestimation of ability could impede proper career development choices. Twenty-three data tables are included, and sample first- and second-order factor scales of the Career Exploration Inventory (CEI) are appended. (TJH)