The anti-inflammatory effects of the methanol extract of the roots of Morinda officinalis (MEMO) (Rubiaceae) were evaluated in-vitro and in-vivo. The effects of MEMO on lipopolysaccharide (LPS)induced responses in the murine macrophage cell line RAW 264.7 were examined. MEMO potently inhibited the production of nitric oxide (NO), prostaglandin E2 and tumour necrosis factor-alpha (TNF-alpha) in LPS-stimulated RAW 264.7 macrophages. Consistent with these results, the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the protein level, and of iNOS, COX-2 and TNF-alpha at the mRNA level, was also inhibited by MEMO in a concentration-dependent manner. Furthermore, MEMO inhibited the nuclear factor kappa B (NF-kappaB) activation induced by LPS, and this was associated with the prevention of degradation of the inhibitor kappaB (IkappaB), and subsequently with attenuated p65 protein in the nucleus. The anti-inflammatory effect of MEMO was examined in rats using the carrageenan-induced oedema model. The antinociceptive effects of MEMO were assessed in mice using the acetic acid-induced abdominal constriction test and the hot-plate test. MEMO (100, 200 mg kg-1 per day, p.o.) exhibited anti-inflammatory and antinociceptive effects in these animal models. Taken together, the data demonstrate that MEMO has anti-inflammatory and antinociceptive activity, inhibiting iNOS, COX-2 and TNF-alpha expression by down-regulating NF-kappaB binding activity.