Histochemical staining with a battery of ten lectins demonstrated differences in lectin binding patterns between seminal vesicle, prostatic central and peripheral zones, and foci of prostate intraductal dysplasia, a putative premalignant lesion. Lectin binding patterns of seminal vesicle and central zone of the prostate were identical except for a single lectin, supporting the concept that these two structures have a common embryologic origin from the wolffian duct. Three of the lectins that bound to central zone were not bound in peripheral zone, indicating a biologic difference between these two regions of the prostate. Dysplasia foci showed markedly reduced binding with all lectins, consistent with impaired processing of glycoconjugates. Lectin binding patterns appear to have value as sensitive markers of difference in terminal differentiation of closely related tissues and of early impairment of differentiated function in lesions that are precursors to carcinoma. Specific patterns of lectin binding provide information on the differential carbohydrate composition of the regions of the prostate.