A procedure for renaturation of heterodimeric platelet-derived growth factor (PDGF-AB) from inclusion bodies of recombinant Escherichia coli using size-exclusion chromatography is described. Either prepurified or crude PDGF-AB inclusion bodies solubilized with guanidinium hydrochloride were subjected to buffer exchange from denaturing to renaturing conditions during chromatography. Renaturation of PDGF-AB involves folding of the solubilized and unfolded molecules into dimerization competent monomers during size-exclusion chromatography and subsequent dimerization of folded monomers into the biologically active heterodimeric growth factor. Optimized conditions result in an overall yield of 75% active PDGF-AB with respect to size-exclusion chromatography and subsequent dimerization. The described approach allows renaturation at high protein concentrations and circumvents aggregation which is observed when refolding is carried out by dilution.