This study was carried out to examine the potency of the three surface components from Porphyromonas gingivalis to stimulate the murine macrophage cell line RAW264.7 to synthesize the pro-inflammatory cytokine tumor necrosis factor alpha(TNF-α) and nitric oxide (NO). Lipopolysaccharide(LPS), lipid A-associated proteins(LAP) and saline-extractable surface-associated material(SAM) were isolated from P. gingivalis 381. TNF-α release into culture supernatants was determined by two-site ELISA. NO production was assayed by measuring the accumulation of nitrite in culture supernatants. Western blot analysis of iNOS and analysis of reverse transcription(RT)-PCR products were carried out. The surface components extracted from this bacterium were almost equally potent in stimulating release of TNF-α and NO by RAW264.7 cells. TNF-alpha that was being measured immunologically was due to activation of TNF-α gene transcription. The present study clearly shows that P. gingivalis surface components fully induced iNOS expression in RAW264.7 cells in the absence of other stimuli. The ability of P. gingivalis surface components to promote the production of TNF-α and NO may be important in the pathogenesis of inflammatory periodontal disease.