Objective: To investigate the effect of Haishengsu, an extract from Tegillarca L. granosa, on the effects and side effects of immunotherapy in patients with advanced renal cell cancer. Methods: Fifty-five patients with renal cell cancer were randomly divided into Haishengsu (n=27, 2.4mg, iv for 15 days) and control group (n=28). All patients were also treated with interleukin-2 (IL-2), interferon-alpha (IFN) and fluorouracil (5-FU). Results: In the Haishengsu group, the prevalence of gastrointestinal reactions to the immunotherapy was lower than in the control group (18.5% vs 64.3%, P <0.01). In comparison with the control group, more patients from the Haishengsu group had increased food-intake (74.1% vs 14.3%, P<0.01), weight gain (77.8% vs 10.7%, P <0.01) or an increase in Karnofsky Performance Status (KPS) score (55.6% vs 17.9%, P<0.01). The remission rate of cancer in the Haishengsu group was higher than in the control group (51.9% and 21.4%, P <0.01). Conclusions: Addition of Haishengsu to the conventional immunotherapy is associated with an increased remission rate in patients with advanced renal cell cancer. Haishengsu was also associated with a reduced rate of gastrointestinal side effects from the immunotherapeutic agents, and an improved the physical functionality of the patients.