The physical interaction between human spermatozoa and the epithelium of the human uterine (Fallopian) tube was investigated in vitro using a variety of techniques. The 'live' observation of human spermatozoa incubated with 1 day old cultures of tubal epithelium demonstrated that spermatozoa can show a strong physical interaction with epithelial cells; contact with the epithelium appeared to be random and there was no evidence of any taxis toward epithelial cells. The physical interaction (or 'binding') was resistant to gentle washing and was maintained following the addition of glutaraldehyde fixative. The intimate nature of the interaction was confirmed ultrastructurally where both spermatozoa and epithelial membranes were observed to be in close apposition. These results are the first descriptions of sperm-epithelial 'binding' in the human. They are similar to other observations made in a variety of non-human mammalian species. It is suggested that this interaction may be an important feature of normal sperm transport in the human uterine tube in vivo.