Using the test scores of more than 1,000,000 students who participated in the Advanced Placement Computer Science (AP CS) exams from 1997 to 2020, this study examined the direction and magnitude of the trends in gender disparity in participation and top achievement in advanced exams. The findings indicated that the male-to-female ratio (MFR) among AP Computer Science (CS) exam participants declined from 4.87 to 2.26 between 1997 and 2020. Similarly, the MFR among top scorers (students who scored 5 out of 5) in any type of AP CS exams declined rapidly, in favor of female students, from 8.00 to 2.14 during the same period. Possible implications of these findings for educators, particularly for AP CS teachers and school counselors, were also discussed in the context of the underrepresentation of females in computing fields.