Numerous investigators have identified, isolated and characterized serum glycoproteins that are claimed to be specifically associated with malignancy. We have carried out serum glycoprotein electrophoresis on polyacrylamide disc gel in 53 breast cancer patients, at diagnosis as well as during and after therapy. Follow-up samples were divided into complete responders (CR) (n = 138) and nonresponders (NR) (n = 44). Glycoprotein electrophoresis showed multiple bands for each sample which were categorized into four groups: albumin, alpha, beta and gamma. The results revealed a decreasing number of CR and increasing number of NR with elevated (as compared to pretreatment levels) albumin fraction glycoproteins. Gamma region glycoproteins showed the reverse pattern to that of albumin region glycoproteins. The alpha and beta region glycoproteins revealed an increasing number of CR having higher values with increase in follow-up duration. In comparison with their pretreatment values CR showed significantly increased (Paired "t" test) values of albumin, alpha and beta region glycoproteins (p < 0.01, p < 0.001 and p < 0.001, respectively) and decreased gamma region glycoproteins (p < 0.001). The albumin, alpha, beta and gamma region glycoprotein levels were comparable between NR and untreated cancer patients. The variations in albumin, alpha, beta and gamma region glycoproteins correlate with treatment response, which might be useful in the treatment monitoring, and prediction of recurrence in breast cancer patients.