Tramadol is commonly used as second step drug of the analgesic ladder. In circumstances where the oral route is unavailable, rectal administration of opioids might be a simple alternative. The aim of this study was to compare the analgesic activity and tolerability of tramadol by oral and rectal administration in a double-blind, double-dummy crossover trial. The study included 60 cancer patients with cancer pain no longer responsive to non-opioid drugs. Each patient initially received oral tramadol 50 mg (drops), followed by tramadol sustained release 100 mg orally, and placebo rectally, or tramadol 100 mg rectally and placebo orally, twice a day, in a randomized sequence, on each of 3 days. Patients were allowed to take 50 mg of oral tramadol by drops as needed (four doses per day, to a maximum of 400 mg/day, including the basal dose given by the oral or rectal route). Pain intensity and relief and symptom scores were recorded every day and at the end of each phase of the crossover. The mean age of the patients was 66.1 years (SD 13.5 years); 36 were female, and 44 completed both periods. Patients dropped out due to adverse effects (15 patients) and refusal (1 patient). No differences in the use of rescue dose of oral tramadol were observed between the groups. No differences in pain intensity and relief scores, or in other symptoms between the two treatments were observed. No differences in treatment efficacy as judged by the clinician (P=0.73), in patient compliance (P=0.35), or in patient satisfaction regarding treatment (P<0.35) were found. No differences in adverse effects were found between the two treatments (25.5%, 13 patients, and 20.4%, 11 patients, with oral and rectal treatment, respectively). The proportion of preferences favored oral administration for both physicians (P=0.0002) and patients (P=0.002). Rectal administration of tramadol appears a reliable, noninvasive alternative method of pain control for patients no longer responsive to non-opioid analgesics, unable to take oral tramadol.