(3 S,14 S)-Petrocortyne A, a lipid compound (a C(46) polyacetylenic alcohol), from marine sponges ( Petrosia sp.) is potently cytotoxic against several solid tumour cells. In this study, we investigated in vitro anti-inflammatory and pro-aggregative effects of petrocortyne A at non-cytotoxic concentrations on various cellular inflammatory phenomena using the macrophage and monocytic cell lines RAW264.7 and U937. Petrocortyne A blocked tumour necrosis factor-alpha (TNF-alpha) production strongly and concentration-dependently in lipopolysaccharide (LPS)-activated RAW264.7 cells and phorbol 12-myristate 13-acetate (PMA)/LPS-treated U937 cells. It also blocked NO production concentration-dependently in LPS- or interferon (IFN)-gamma-treated RAW264.7 cells. Among the migration factors tested, the compound selectively blocked the expression of hepatocyte growth factor/scatter factor (HGF/SF). On the other hand, as assessed by a cell-cell adhesion assay, petrocortyne A did not block the activation of adhesion molecules induced by aggregative antibodies to adhesion molecules, but suppressed PMA-induced cell-cell adhesion significantly. Intriguingly, petrocortyne A induced U937 homotypic aggregation following long exposure (2 and 3 days), accompanied by weak induction of pro-aggregative signals such as tyrosine phosphorylation of p132 and phosphorylation of extracellular signal-related kinase 1 and 2 (ERK 1/2). Petrocortyne A may thus inhibit cellular inflammatory processes and immune cell migration to inflamed tissue.