In 40 healthy subjects, in 47 non-cancer patients, and in 142 cancer patients, perchloric acid soluble glycoproteins (PASG) and hexosamines were determined to investigate their tumor specificity and correlation with the tumor mass. Cancer patients were divided into three subgroups: CI, no evidence of cancer (after radical surgery); CII, locoregional disease; CIII, widespread metastatic disease. There was no statistically significant difference in PASG among normals, non-cancer and CI patients; hexosamines in non-cancer and in CI patients were higher (P less than 0.002) than in normals; both PASG and hexosamines were significantly higher in CII and CIII patients than in normals (P less than 0.001). In the CI group, 62% of patients who relapsed within 10 months after surgery had high hexosamine values, whereas 69% of patients who did not relapse showed normal levels (P less than 0.05). PASG and hexosamines significantly increased with cancer progression and decreased when objective response to treatment was achieved. They are not tumor specific, but seem to be related to the tumor burden; hexosamines seem to have some prognostic value.