The aim of this study was to examine the effects of beta-D-xyloside (XYL), a compound which interferes with stromal proteoglycan (PG) synthesis, on androgen induced growth of the lateral prostate (LP). Young male guinea pigs were castrated at 3 weeks of age and divided into three groups 6 weeks after castration. In group one, the animals were injected subcutaneously daily with 80 mg/kg of XYL, followed 3 days later by a daily dose of 10 mg/kg of dihydrotestosterone (DHT) for 2 more weeks. The second group served as control and received DHT only. In the third group, animals were treated first with XYL, like those in group one, and then followed by DHT alone for 2 weeks to check reversibility of the XYL effect. At the end of the experiment, the lateral prostate was removed and processed for morphological and cytochemical examination. The results showed that XYL inhibited the DHT stimulated growth of the lateral prostate. The fibroblasts showed a dilated granular endoplasmic reticulum filled with granular substances. In the interstitial spaces, there was a drastic increase in Cuprolinic Blue (CB) positive filaments and polygonal granules believed to be PGs or glycosaminoglycans (GAGs). Their number was much greater than the control. The distribution and density of the collagen fibers appeared similar to the control. The secretory alveoli were lined by epithelium with few secretory granules of low electron density and a larger number of clear vesicles. There was a slight reduction in glycoconjugate reactivities in the epithelial cells. The lectin binding patterns and the structural features were comparable between the control and recovery groups, indicating the XYL effects were reversible. The results suggest that stromal PG biosynthesis may play a role in epithelial function and an altered stromal matrix would hamper the effects of DHT on the target organ.