Objectives: To determine maternal–fetal transplacental passage of vancomycin in the ex vivo human placental perfusion model.Methods: Six term placentas were collected immediately after delivery and perfused with physiologic medium using the single cotyledon perfusion system. Vancomycin was added to the maternal medium and perfused through the maternal circulation of the cotyledon. Over a 1-h period in an open system, samples of the perfusate were collected at defined intervals from the fetal venous catheter and from the maternal effluence to assess vancomycin transfer. Thereafter, the system was closed for 1–5 h to establish accumulation. Transport fraction and clearance indexes were calculated by perfusing antipyrine C14 (positive control). Vancomycin was estimated by high pressure liquid chromatography and antipyrine C14 concentration was determined by liquid scintillation.Results: Mean vancomycin maternal peak and trough concentrations ranged from 30.0 to 51.5 µg/ml and 7.7 to 16.4 µg/ml, respectively. Clearance indexes were minimal with a mean peak range of 0.000–0.080 and a mean trough range of 0.00–0.17. For each placenta, transport fraction for antipyrine C14 was > 1.85 with a single pass of > 40%. No accumulation of vancomycin was noted when the system was closed for 1–5 h. The mean peak clearance index was zero after perfusing the placenta for up to 5 h with 35.8 µg/ml of vancomycin.Conclusion: Transplacental passage of vancomycin was minimal in the ex vivo human placental perfusion model, with no detectable accumulation.