In October 1999, CDC, in collaboration with other federal partners, initiated the National Plan to Eliminate Syphilis in the United States. Syphilis elimination is defined as the absence of sustained transmission (i.e., no transmission after 90 days of the report of an imported index case). The national goals for syphilis elimination are to reduce the annual number of primary and secondary (P&S) syphilis cases to <1,000 cases (rate: 0.4 per 100,000 population) and to increase the number of syphilis-free counties to 90% by 2005. To characterize the epidemiology of syphilis in the United States, CDC analyzed national notifiable disease surveillance data for 2000-2001. This report summarizes the results of that analysis, which indicate that the number of reported cases of P&S syphilis increased slightly in 2001. This increase occurred only among men; the number of P&S syphilis cases continued to decline among women and among non-Hispanic blacks. The available data indicate that syphilis cases occurring among men who have sex with men (MSM) contributed to the increase in cases. The data suggest that, although efforts to reduce syphilis among women and non-Hispanic blacks appear effective and should continue, efforts to prevent and treat syphilis among MSM need to be improved.