The factors that affect the progression of prostatic carcinoma are poorly understood, but it is known that carbohydrateantigens on the tumour cell surface play a role in the transforming and metastatic processes. The present reportaimed to perform a comparative, lectin-histochemical study of benign and carcinomatous prostates, using a battery oflectins, in combination with monoclonal antibodies against Lewis antigens, and a semi quantitative study, to investigate thechanges in glycosylation patterns that occur in prostatic carcinoma. Blocks from 27 necropsy cases of prostatic carcinomawere sectioned and stained with H+E, fifteen biotinylated lectins chosen to probe for a wide range of oligosaccharidesequences within several categories of glycoprotein glycans, using a lectin-biotin avidin-peroxidase method, and monoclonalantibodies against Lewisa, sialyl Lewisa and sialyl Lewisx antigens. The glycophenotype of prostatic carcinoma differedfrom that of the noncancerous prostate in revealing more intense staining with the following lectins (AAA, UEA-1,DBA, WFA, VVA, HPA, BSA-1B4, MPA, ECA, AHA, and CTA), while the binding patterns of (GNA and NPA) were almostsimilar in both prostatic carcinoma and the noncancerous prostate. Lewis antigens are found to be expressed in prostatic carcinomasbut not in the noncancerous prostate. The observations of this study suggest that the gylcophenotype of transformedprostatic cells was modified. It showed a moderate increase in, and changing patterns of, fucosylation and galactosylation,increased branching of side chains and sharp rise in 2 deoxy, 2 acetamido galactosylation and masking process by sialylation,especially by α2-3 and α2-6 linkages. All these changes in the glycosylation pattern of the transformed prostatic cellswere observed on O-glycans, no changes were observed on N-glycans.