Human pigment epithelium-derived factor (PEDF), a neurotrophic factor, is the most potent natural inhibitor of angiogenesis. To produce the active PEDF, the gene coding for the human PEDF protein was expressed in E. coli. The rPEDF protein was expressed at 457 mg l(-1) as a soluble protein. The yield of purified GST fusion protein was 14 mg l(-1). Purified rPEDF inhibited tube formation in endothelial cells.