In 2004, Florida accounted for 11% of the total number of acquired immunodeficiency syndrome (AIDS) cases in the United States, ranking third behind New York and California. Florida also had the second-highest reported AIDS diagnosis rate (behind New York). During 2004, non-Hispanic blacks accounted for 14% of the Florida population but 52% of the 77,421 persons in Florida living with human immunodeficiency virus (HIV)/AIDS. This report describes trends in diagnoses of HIV/AIDS cases that occurred among blacks during 1999-2004 and were reported to the Florida Department of Health. These data indicate that, during 1999-2004, the annual rate of HIV/AIDS diagnosis among blacks decreased more than the rates among other racial/ethnic groups. To examine possible explanations for this decline, HIV/AIDS diagnosis rate trends were compared with trends in gonorrhea diagnosis and publicly funded HIV testing in Florida. The results indicated that gonorrhea diagnosis rates also decreased among blacks in Florida during 1999-2004, whereas the number of HIV tests increased. These findings suggest that HIV/AIDS diagnoses in blacks might be associated with a reduction in high-risk sexual behavior and that the decline was not the result of less testing.