The effect of procyanidolic oligomers (OPC) was studied on mesenchymal cells in culture: human skin fibroblasts (FB) and porcine aorta smooth muscle cells (CML). In presence of OPC part of the freshly seeded FB did not attach. There was no significant effect on the attachment of CML. Proliferation of FB was also slowed down in a dose-dependent manner. Proliferation of CML-s was also decreased, but much less than for FB-s. The detachment of the cells was also studied by adding trypsin to previously attached cells. Detachment of FB-s was strongly inhibited in presence of OPC in a dose-dependent manner. Much less effect was seen on CML. It appears therefore that OPC may interact with some components of the FB cell membrane and modify the attachment, proliferation and detachment of these cells. The only cell kinetic parameter significantly influenced by OPC for CML was their rate of proliferation. This may be due to the different constitution of the CML cell surface as compared to the FB cell surface.