48 primiparae received epidural analgesia in labor with 10 ml of 0.125% bupivacaine with epinephrine 1:800 000, and then were divided in 4 equal groups (n = 12) to receive one of the following: 5 ml saline (B); 100 mug of fentanyl (BF); 150 microg of clonidine (BC); 75 microg of clonidine and 50 microg of fentanyl (BCF). All the patients had satisfactory analgesia. Onset was similar in the 4 groups but the duration of analgesia was significantly prolonged by the addition of either 100 microg of fentanyl or 150 microg of clonidine (respectively 89.8 min and 92.5 min vs 62.5 min) (P < 0.0001). The addition of both clonidine (75 microg) and fentanyl (50 microg) produced a considerably prolonged analgesia (177.5 min) (P < 0.0001). No episodes of bradycardia were observed. Hypotension, reversed by i.v. ephedrine, occurred in 2 patients of BCF group and in 1 patient of BF and BC groups. Only patients receiving fentanyl had pruritus. Both fentanyl and clonidine produced sedation, but both incidence and severity were greater with the mixture. No differences in neonatal outcome assessed by Apgar scores and NACS, were observed.