The behaviour of human spermatozoa was observed during incubation with epithelial cells isolated from the isthmic and ampullary sections of human uterine (Fallopian) tubes. During incubation, spermatozoa were observed to bind to the epithelial cells of the tube (the endosalpinx), and individual spermatozoa attached and detached at intervals. The kinematic characteristics of spermatozoa during these behaviour patterns were determined. The results showed that detached spermatozoa typically had an increased curvilinear velocity and amplitude of lateral head displacement, accompanied by a decrease in their linearity. Significantly (P < 0.01) more of the detaching spermatozoa were hyperactivated than were spermatozoa prior to attachment for both isthmic (35.3 +/- 5.5 versus 4.0 +/- 3.3%; mean +/- SEM) and ampullary (26.0 +/- 7.0 versus 2.0 +/- 1.4%) regions. Incubation with epithelial cells from either region produced no differences in any category of sperm behaviour. Furthermore, there was no significant difference between regions in the amount of time spermatozoa spent bound (33.6 +/- 12.9 and 20.6 +/- 3.0 s for isthmic and ampullary tissue respectively). These results support the hypothesis that hyperactivation may assist spermatozoa in breaking connections with epithelial cells.