Anti-tumor efficacies of a red ginseng preparation (RGP) and a cytolase-treated red ginseng preparation (Cytolase-RGP) in an in vitro cytotoxicity assay and in nude mice xenografted with human colon adenocarcinoma (SW480) cells were investigated. The immune-enhancing effect of the preparations was also assessed using a carbon-clearance test. The concentrations of protopanaxadiols (including Rb1) and protopanaxatriols (including Rg3) were much higher (1.42-3.43-fold) in Cytolase-RGP than in RGP. RGP and Cytolase-RGP were cytotoxic in vitro to SW480 in a dose-dependent manner, exhibiting $IC_{50}$ values of 255 and 1,090 ${mu}g/mL$, respectively. In vivo, the 4-week application of 300 mg/kg RGP or Cytolase-RGP suppressed tumor growth in tumor-bearing mice, decreasing the tumor weight and volume by 15.6-19.3 and 24.4-27.1%, respectively. In the carbon-clearance assay, a 7-day treatment of RGP or Cytolase-RGP at a dose of 300 mg/kg enhanced the phagocytic index of blood macrophages by 307 and 402% of control value, respectively. The results suggest that Cytolase-RGP is superior to RGP in SW480 tumor-suppressive efficacy, and that the increased antitumor activity of Cytolase-RGP might be due to the improved immunomodulatory activity, rather than due to any increase in the cytotoxic activity.