Natural killer (NK) cells account for 70% of the leukocytes in the mucosal lining of the uterus (the decidua) in the first trimester of pregnancy. They are CD56superbright granulated cells expressing a repertoire of Killer-cell Immunoglobulin-like Receptors (KIR) skewed towards recognising HLA-C, which is the only classical class I MHC found on placental trophoblast cells. The function of decidual NK cells is not yet known, but there is evidence to suggest that they are involved in mediating trophoblast invasion into the decidua and modifying maternal spiral arteries to increase blood flow to the placenta. In order to characterise decidual NK cells and to understand their interactions with other cells at the maternal–foetal interface, it is useful to be able to isolate these cells. Here, we describe methods for the isolation and culture of decidual NK cells, decidual stromal cells and trophoblast cells from human first trimester tissue samples.