Twenty-six women with uncomplicated pregnancy at term were selected for the study. Nine had spontaneous vaginal delivery without medication, 8 elective caesarean section under epidural and 9 under general anaesthesia. The results clearly demonstrate that newborns have lower lymphocyte β2-adrenoceptor density than their mothers. In vaginally delivered newborns the lymphocyte β2-adrenoceptor density was 38%, in the caesarean section group with general anaesthesia 27%, and with epidural anaesthesia 22% lower than in the corresponding mother group. Vaginally delivered newborns have lower lymphocyte β2-adrenoceptor density than those delivered by caesarean section. A plausible explanation is the down-regulation of the β2-adrenoceptors during labour and delivery.