Bioavailability of ibuprofen (15 mgkg-1) from oral and suppository dosage forms was investigated. Three different combinations of PEG 4000 and 1000 and theobroma oil were used as suppository bases. Oral administration gave higher values for mean residence time (MRT) and absolute bioavailability (F) compared to suppository dosage forms. The theobroma oil base was associated with lower maximum plasma concentration (cpmax), area under the concentration time curve (AUC) and F values compared to the other bases but differences were not significant (P greater than 0.05). Ibuprofen appears to be strongly retained by the lipophilic base, thereby limiting its diffusion through the rectal mucosal membrane. The absorption profile was slightly improved for the three PEG combination bases but were inferior to oral dosing. It is suggested that the relatively smaller size of the rectal mucosal membrane compared to the small intestine was primarily responsible for limiting the rate/extent of ibuprofen absorption. The absorption profile from the suppository preparations may be enhanced by the appropriate selection of the bases and their additives.