Changes in the peripheral blood leucocyte count, lymphocyte subpopulations, and in 'in vitro' responses of lymphocytes to phytohaemagglutinin and tuberculin after induced labour were investigated in 10 normal parturients and their newborns. Every other parturient was given segmental epidural analgesia at level T 10-12 for pain relief during the first stage of labour. The remaining mothers served as controls. The results of blood samples taken from the mothers before induction of labour and from the newborns immediately after delivery served as basal values against which the results of samples drawn on the 1st and on the 5th day following delivery were compared. A significant (p less than 0.05) increase from the basal values in the total leucocyte count after delivery was found only in those mothers not given epidural analgesia and in their newborns. Similarly, a significant (p less than 0.01) decrease in the T cell count characterized by both E rosette formation and acid alpha-naphthyl acetate esterase staining was found in the peripheral blood only in the mothers (but not the newborns) without epidural analgesia. The differences between the research groups were not, however, significant. The lymphocyte response to phytohaemagglutinin on the 1st and on the 5th day after delivery was also significantly (p less than 0.05) lower in the newborns of the mothers not given epidural analgesia than in those of the mothers given it. The present results show that the depression induced by the stress of parturition in some parameters of cell-mediated immunity of mothers and newborns can be at least partly prevented by using segmental epidural analgesia.