After declining steadily for 10 years, the number of reported cases of primary and secondary (P&S) syphilis more than doubled in New York City (NYC) from 117 in 2000 to 282 in 2001. The increases have occurred primarily among men who have sex with men (MSM). Of particular concern is the high proportion of syphilis cases among MSM who also have human immunodeficiency virus (HIV). This report summarizes 2001 P&S syphilis data for NYC and compares it with surveillance data for 1999 and 2000; findings indicate a substantial increase in the number of syphilis cases among MSM. These data suggest increases in high-risk sexual behavior among some MSM and underscore the importance of coordinating efforts between the MSM community public health officials, and health-care providers to strengthen HIV-prevention efforts.