Although syphilis occurs infrequently among Canadian and American women, global antenatal screening is still warranted. The reason is that congenitally acquired syphilis is serious, yet largely preventable. Those women at highest risk for the disease seem to be crack and cocaine users, as well as those without antenatal care. These women should be screened for syphilis during the first and early-third trimesters, whenever possible, or at the time of delivery. HIV testing should be routinely recommended. Syphilis is diagnosed using microscopy and/or serologic testing. Although nontreponemal serology (VDRL and RPR) is acceptable as the initial screening test, sensitivity and specificity for syphilis vary between 60 and 75 percent and 84 and 99 percent, respectively. These are also many causes of false-positive test results. Treponemal serology (FTA-ABS and MHA-TP) are used to confirm nontreponemal tests. The only acceptable treatment of syphilis during pregnancy is penicillin. For those with disease of less than 1 year's duration, it is suggested that two doses of benzathine penicillin G (2.4 million units I.M.) be administered 1 week apart. Disease of greater or unknown duration requires a longer, modified regimen. Serious adverse reactions to therapy are rare, and penicillin-allergic mothers can be skin tested, followed by desensitization if required. Exactly how HIV infection modifies the detection and treatment of syphilis in pregnancy is unclear. Treatment of HIV-infected women with syphilis is presently no different than non-HIV patients, unless invasion of the central nervous system is suspected.