In the present study we tested numerous soluble immunological parameters (soluble Interleukin 2 receptor, Beta 2 microglobulin, Neopterin, soluble CD8 antigen, gamma Interferon and alpha Tumor Necrosis Factor) in sera obtained from 18 advanced cancer patients during subcutaneous treatment with recombinant Interleukin 2. The treatment cycles consisted of a dose of 9 x 10(6) IU/m2 twice daily for 2 days followed by 1.8 x 10(6) IU/m2 twice daily for 5 days/week during 6 weeks. Even before therapy, neoplastic patients had higher levels of soluble Interleukin 2 receptor than a group of healthy subjects. Moreover, basal soluble CD8 antigen levels showed significant differences (p < 0.01) in patients with different clinical responses (responders and non-responders). During treatment we observed a fast increase (in the first or second week) of all parameters considered; soluble Interleukin 2 receptor and soluble CD8 antigen were the markers that were best related to the course of immunotherapy. In conclusion, monitoring recombinant Interleukin 2 immunotherapy with immunological parameters in serum seems to be of interest. However, more data are necessary to confirm the real value of the single markers.