Anticancer effects of Aloe on sarcoma 180 in ICR mouse or human cancer cells were determined. Sarcoma 180 cells were inoculated subcutaneously into male ICR mouse to determine effect of Aloe on tumor gowth, or inoculated intraperitoneally into male ICR mouse to determine effect of Aloe on life span prolongation, followed by oral administration of Aloe vera(10 mg/kg/day, 50 mg/kg/day) or Aloe arborescens(10 mg/kg/day, 100 mg/kg/day) once a day for 14 days. The administration of Aloe vera or Aloe arborescens did not suppress tumor growh. However the life span of ICR mouse was prolonged to 19%(p<0.05), 22%(p<0.05) and 32%(p<0.05) by administration of Aloe vera 10 mg/kg/day, Aloe vera 50 mg/kg/day, and Aloe arborescens 100 mg/kg/day, respectively. To determine anticancer effect of Aloe in vitro, Aloe extract was added to the culture of human gastric cancer cells(SNU-1) and colorectal cancer cells(SNU-C2A), and concentration of Aloe to inhibit cancer cell growth was determined using MTT(3-[ 4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) cytotoxicity assay. High $ID_{50}$ values of Aloe vera and Aloe arborescens against gastric cancer cell line(SNU-1) and colorectal cancer cell line(SNU-C2A) suggest that Aloe gel does not have anticancer effect on these specific human cancer cells although high concentration of Aloe inhibited growth of human cancer cells significantly.