From 2001-2006, the rate of primary and secondary (P&S) syphilis (cases/100,000 population) in the United States increased from 2.1 to 3.3. Newly available data on sex of partners show that 64% of P&S syphilis occurred in men who have sex with men in 2006. From 2003-2006, the P&S syphilis rate in women increased from 0.8 to 1.0, and the rate of congenital syphilis (cases/100,000 live births) increased from 8.2 in 2005 to 8.5 in 2006. Providers and public health staff need to know the sex of partners of patients with syphilis if they are to utilize the appropriate interventions.