This study has examined the expression of adhesion molecules by uterine-specific CD56bright CD16-CD3- large granular lymphocytes using flow cytometry and immunohistology. Data are compared with those obtained after IL-2 stimulation and with peripheral blood CD56+ cells. We have found that decidual CD56bright cells strongly express three fibronectin receptors, alpha 4 beta 1, alpha 5 beta 1, and alpha 4 beta 7. The HML-1 antigen is also expressed. The beta 2 integrins are also found on decidual CD56+ cells although, apart from CD11c, these are present at levels lower than those of corresponding cells in blood. After IL-2 stimulation there is a considerable increase in CD11a/CD18 expression on CD56bright cells. Both ICAM-1 and NCAM are found on CD56bright cells at higher levels compared to those of peripheral blood CD56+ cells. This pattern of expression of beta 1 and beta 2 integrins and members of the immunoglobulin superfamily must have important implications in the behaviour of decidual LGL. These adhesion molecules are also likely to be important in the recruitment and retention of CD56bright LGL in the decidual microenvironment particularly as the specialised decidual extracellular matrix and uterine LGL appear concomitantly at the time of implantation.