B-vitamins possess antinociceptive and antiinflammatory activity. The rat tail pressure test was used to examine whether a mixture of the vitamins B1, B6, and B12, clinically used as Neurobion, has antinociceptive activity itself or potentiates the effect of the non-steroidal antiinflammatory drug (NSAID) diclofenac on carrageenin-induced hyperalgesia. Only the highest dose of the vitamin mixture (667 mg/kg B1 and B6, 6.7 mg/kg B12 p.o.) exhibited antinociceptive activity. Nevertheless, lower doses which alone were lacking in activity (100-250 mg/kg B1 and B6, 1-2.5 mg/kg B12 p.o.) dose-dependently potentiated the antinociceptive of diclofenac. This result supports the clinical experience of a reduced need for diclofenac when B-vitamins are administered concomitantly.