Herpes simplex virus (HSV) infection commonly causes "cold sores" (HSV type 1 [HSV-1]) and genital herpes (HSV-1 or HSV type 2 [HSV-2]); HSV infection in newborns can result in death or permanent disability. During November 2000-December 2011, a total of 11 newborn males had laboratory-confirmed HSV infection in the weeks following out-of-hospital Jewish ritual circumcision, investigators from the New York City Department of Health and Mental Hygiene (DOHMH) learned. Ten of the 11 newborns were hospitalized; two died. In six of the 11 cases, health-care providers confirmed parental reports that the ritual circumcision included an ultra-Orthodox Jewish practice known as metzitzah b'peh, in which the circumciser (mohel, plural: mohelim) places his mouth directly on the newly circumcised penis and sucks blood away from the circumcision wound (direct orogenital suction). In the remaining cases, other evidence suggested that genital infection was introduced by direct orogenital suction (probable direct orogenital suction). Based on cases reported to DOHMH during April 2006-December 2011, the risk for neonatal herpes caused by HSV-1 and untyped HSV following Jewish ritual circumcision with confirmed or probable direct orogenital suction in New York City was estimated at 1 in 4,098 or 3.4 times greater than the risk among male infants considered unlikely to have had direct orogenital suction. Oral contact with a newborn's open wound risks transmission of HSV and other pathogens. Circumcision is a surgical procedure that should be performed under sterile conditions. Health-care professionals advising parents and parents choosing Jewish ritual circumcision should inquire in advance whether direct orogenital suction will be performed, and orogenital suction should be avoided.