Intrathecal sufentanil provides approximately 2 h of excellent labor analgesia with minimal motor blockade. Epidural sufentanil has received less scrutiny but may provide the same benefits as intrathecal sufentanil. In this study, we compared epidural sufentanil 40 microg after a lidocaine with an epinephrine test dose with intrathecal (i.t.) sufentanil 10 microg with respect to onset and duration of analgesia, degree of motor block, side effect profile, and mode of delivery. Seventy ASA physical status I or II parturients in early labor (< or = 4 cm cervical dilation) were randomized to receive either i.t. sufentanil 10 microg with a combined spinal-epidural technique (CSE) or epidural sufentanil 40 microg (e.p.) after epidural catheter placement and testing with 3 mL of 1.5% lidocaine with epinephrine (15 microg). After the administration of analgesia, pain scores and side effects were recorded for each patient at 5, 10, 15, 20, and 30 min, and every 30 min thereafter, by an observer blinded to the technique used. The study period was completed when the patients requested additional analgesia. All patients, except one, achieved adequate analgesia with the initial study dose and satisfactorily completed the study. There were no demographic differences between the two groups. Pain relief was rapid for all patients; pain scores were significantly lower at 5 and 10 min in the i.t. group versus the e.p. group. The mean duration of analgesia was similar between the e.p. group (127 +/- 40 min) and the i.t. group (110 +/- 48 min). No patient experienced any motor block. Side effects were similar between the two groups, except for pruritus-both the incidence and severity were significantly more profound at 5, 10, 15, 20, and 30 min in the i.t. group. There was no difference in time from analgesic to delivery, incidence of operative or assisted delivery, or cervical dilation at the time of redose. For early laboring patients, epidural sufentanil 40 microg after a lidocaine test dose provides analgesia comparable to that of i.t. sufentanil 10 microg with less pruritus. CONCLUSIONS We compared the efficacy and side effects of intrathecal sufentanil with epidural sufentanil with a local anesthetic test dose for analgesia during labor. Analgesia was equally good, although the intrathecal group experienced more itching.