Purpose: PCDGF (PC cell-derived growth factor), also called progranulin, is a Mr 88,000 glycoprotein precursor of granulin. It is a novel growth factor that stimulates cell proliferation, confers epithelial tumorigenesis, and promotes tumor invasion. Here we investigate the potential of PCDGF as a therapeutic target for prostate cancer. Experimental Design: We studied the expression of PC-DGF in invasive prostate cancer, adjacent high-grade prostatic intraepithelial neoplasia (PIN), and benign prostate tissue from 99 human prostate specimens. The level of PC-DGF expression was correlated with various clinicopathological characteristics. Results: Normal prostate tissue did not express (53/99), or expressed low levels (46/99) of PCDGF. In the 46 normal prostate specimens that expressed PCDGF, most of them had less than 10% of cells expressing PCDGF. PCDGF expression could be detected in more than 50% of cells in all specimens of PIN and invasive prostate cancer. The expression of PCDGF in normal prostate tissue was much less intense and in a smaller fraction of cells than in PIN and invasive adenocarcinoma (P < 0.0001). There was no correlation of PCDGF expression with age, Gleason score, pathological stage, status of lymph node metastasis, extraprostatic extension, perineural invasion, surgical margins, and vascular invasion. Conclusions: Our data suggest that the induction of PCDGF expression occurs during the development of PIN. PCDGF may be a new molecular target for the treatment and prevention of prostate cancer.