In our previous study, Soamsan, a traditional Oriental medicine, was shown to enhance the induction of antigen-specific immune responses, and it was speculated that the enhancing activity might be closely associated with glycoproteins contained within the medicine. To elucidate this speculation, protein samples from each component, used in the preparation of Soamsan, were obtained and their immune stimulating activities were tested with mouse splenocytes. All the samples markedly enhanced the lymphocyte proliferation and cytokine secretion by the mouse splenocytes. In particular, the enhancement was significantly higher with the protein sample treatments than with those of the original crude sample. Furthermore, the pronase E- and $NaIO_4$-mediated inhibition of splenocyte-stimulation activity of the protein samples clearly supported that glycoproteins are the main class of active ingredients responsible for the lymphocyte stimulating activity of the samples. Consequently, our findings suggest that glycoproteins might have a pivotal role in Soamsan-mediated immune modulation, although the in vivo effect of the glycoproteins should be further elucidated.