Polyhydroxyethylmethacrylate (PHEMA) microcarriers in a size range of 150-250 microns were prepared by a suspension polymerization in an aqueous phase containing magnesium oxide. The hydroxyl groups on the PHEMA microcarriers were activated by cyanogen bromide. In order to improve cell attachment, cell-adhesive proteins, namely, collagen and fibronectin were immobilized onto PHEMA microcarriers. The nonspecific adsorption values for collagen and fibronectin were 0.10 mg collagen/g PHEMA and 0.044 mg fibronectin/g PHEMA, respectively. Collagen and fibronectin immobilization on PHEMA microcarriers were studied at different pH by using single protein solutions containing different amounts of proteins, at a constant temperature of 20 degrees C. The maximum immobilizations were 0.85 mg collagen/g PHEMA (at pH: 9.5) and 0.52 mg fibronectin/g PHEMA (at pH: 7.4). Hepatocyte attachment onto these biologically modified PHEMA microcarriers was studied. Hydrophilic PHEMA microcarriers did not support cell attachment. High hepatocyte attachment yields (up to 75% surface coverage) were observed on collagen and fibronectin immobilized PHEMA microcarriers.