Postatrophic hyperplasia (PAH) of the prostate is a non-neoplastic glandular alteration sometimes confused with prostate carcinoma (PCa) histologically. Although atrophy had long been considered a possible precursor lesion for PCa, a theory that has been largely dismissed, the topographical relationship of PAH to PCa has not been studied systematically. Whole mount sections from 272 randomly selected radical prostatectomy (RP) specimens (T1c, 2, 3, N0, 1) and 44 cystoprostatectomy (CP) specimens (28 with incidental PCa) were assessed for the presence, location, and number of foci of PAH, and then were correlated with the presence and location of PCa foci. PAH was identified in 86 (32%) RP and in 12 (27%) CP specimens. The distribution of PAH foci: peripheral zone (91%), transition zone (8%) and central zone (1%), and apex (49%), mid (39%), and base (12%). For RP specimens, 183 foci of PAH showed no atrophy in a mirror image area of the prostate opposite the focus of PAH. Of the foci, 33% showed PCa either within or within 2 millimeters of the focus of PAH. For the mirror image area without PAH, PCa was identified either within or within 2 millimeters of the area in 40% (p = 0.19). The frequency of PAH in CP specimens and its relationship to incidental PCa was not significantly different from that of RP specimens (p = 0.60, chi square). Therefore, PAH is a relatively common lesion, most often seen in the peripheral zone of the apical third of the gland. PAH does not appear to have any association with PCa.