Evidence has now accumulated that heparin can significantly affect immune response including allergic inflammation. Cell motility is supposed to be very crucial in this process. Thus the aim of our study was to investigate whether heparin is a chemoattractant for some inflammatory cells and is also capable of influencing chemotaxis induced by typical chemoattractants. Peripheral blood mononuclear cells (PBMCs) and neutrophils from 10 healthy subjects were obtained by gradient centrifugation. Chemotaxis assays towards either heparin (molecular weight 16 kDa) or low molecular weight heparin--fraxiparine (molecular weight 5 kDa) were performed in Boyden chambers. We found that both heparin molecules are chemoattractants for both PBMCs and neutrophils in the wide concentration range (0.1-2000 microg/ml). However, maximal chemotaxis was observed at concentrations 50-100 microg/ml (fraxiparine) and 1-50 microg/ml (heparin). We also found that fraxiparine was able to significantly increase chemokinesis and decrease chemotaxis in the gradient of both fMLP and IL-8. These results indicate that heparin is a potent regulator of cell migration.