To maintain a healthy pregnancy, the exchange of substances between mother and fetus is vital. All transport takes place through the placenta, which is a temporary organ that serves its purpose from the implantation of the blastula to the birth of the term fetus, supplying nutrients, gas and waste transport between the maternal blood and the developing fetus. The placenta consists of cells of both maternal and fetal origin and forms a complex barrier between the maternal and fetal blood that allows for passage of different molecules, either by passive or facilitated diffusion or active transport systems. This makes placental transport studies interesting when investigating fetal exposure to foreign or innate substances. It is possible to investigate the transport of selected substances across the human placenta using the human term placenta perfusion model. Perfusion models are very useful in studying effects and actions of various live tissues, in order to extrapolate the findings to a real life exposure situation. Simplified models make validated inter-laboratory comparison and extrapolation to the in vivo situation critical. In this chapter the focus is on placental perfusion studying environmentally ubiquitous harmful substances. Inter-laboratory comparisons have confirmed the reproducibility of the system [1]. Benzo[α]pyrene (BaP) is a highly carcinogenic substance produced by everyday combustion. The transport kinetics of this substance is interesting, as it is influenced by the concentration and species-origin of albumin in the medium. Albumin functions as a transport molecule for BaP by keeping it suspended in the medium and loading BaP into the placental barrier cell-layer closest to the maternal blood (the syncytiotrophoblast) [2]. The placental transport of three polybrominated diphenyl ethers: BDE-47, BDE-99 and BDE-209 showed decreased transfer across placenta with increased bromination of the molecule [3]. The placental transport of two non-dioxin-like polychlorinated biphenyls (PCBs) (PCB52 and 180) were studied in the placental perfusion and in the BeWo b30 clone monolayer transfer model, a cell assay using a human trophoblast cell line. The transfer of PCB 180 was more rapid in both systems, and PCB 52 adhered more to the placental tissue [4].