An embryo transfer catheter (10) is described comprising an outer catheter body (12) having first and second lumens (14, 16). The second lumen (16) is adapted to receive an internal catheter (not shown) with a single lumen which, in use, will allow passage of an embryo or embryo-containing cannula (not shown) into the uterus (18) of the recipient. An inflatable balloon (20) is provided at a distal end of the first lumen (14). The inflatable balloon (20) is designed to be as small as possible in its inflated condition whilst still being retained in the uterus (18). The shape of the balloon (20) is adapted in its inflated state to conform to just the lowest part of the uterus (18). The aim in designing the balloon (20) as small as possible is to leave as much endometrium accessible to the embryo for implantation as possible, and to occupy as little volume as possible within the uterine cavity and to exert as little pressure as possible to avoid causing contractions, whilst still being retained in the uterus (18).
