For HIV-infected women who have not received antiretroviral treatment or transmission prophylaxis in pregnancy, starting antiretrovirals in labor or soon after birth can still decrease the risk of perinatal transmission. There is, therefore, potential benefit in conducting rapid HIV testing in labor, but hospitals are seldom prepared to conduct such testing. We compared protocols for rapid HIV testing at 2 hospitals to determine what proportion of women had results back early enough to intervene if results had been positive. Hospital A initially used HIV enzyme-linked immunosorbent assays (ELISAs) and changed to using rapid tests (eg, Single Use Diagnostic System [SUDS]); hospital B used only the SUDS. With use of the SUDS in hospital A, results were reported more quickly than with the ELISA protocol in the same hospital (P < 0.0001). Comparing use of the SUDS in the 2 hospitals, test results were available more quickly in hospital A than hospital B (P < 0.05), which resulted in hospital A having more results reported prior to delivery (64% vs. 38%, P < 0.05) and within 12 hours postdelivery (94% vs. 73%, P < 0.05). If HIV testing in labor is to have its maximum effect on decreasing the risk of perinatal HIV transmission, hospitals need to institute rapid HIV testing, but protocols must ensure that results are available as quickly as possible.