Two types of purified samples, water-soluble (sample A; M. W, 1.2 x 10(6) dalton) and water-insoluble (sample C; M. W., 1.0 x 10(6) dalton) samples, were obtained through consecutive separation processes from the culture broth of Ganoderma lucidia mycelium. It was found that both samples from the culture broth were very effective in inhibiting the growth of several human cancer cell lines, having a 93-85% growth inhibition on Hep3B, AGS and A549 with the least cytotoxicity on the normal human lung cell line, WRL68 of less than 25% the highest supplementation concentration of 1.0 mg/l. In general, the sample C showed greater inhibition of cancer cell growth than the sample A. The same trend was also observed in antimutagenicity using the Chinese hamster ovary cell line (CHO test) or Salmonella typhimurium (Ames test). The CHO test showed that sample C had higher antimutagenicity on mutagens 4NQO or MMNG than sample A (approximately 40% vs approximately 25%). The percentage of antimutagenicity from the Ames test was lower than that from the CHO test, possibly due to the difference in the sensitivity of mutagens. The water-insoluble sample greatly enhanced the growth of the human T cell line (H9) up to 1 x 10(5) with sample supplementation at 1.0 mg/l concentration from 4.3 x 10(4) without sample supplementation as well as improved the secretion level of both IL-6 and TNF-alpha up to 100 pg/ml from approximately 40 pg/ml without sample supplementation. The kinetics of response to the immune cell growth was illustrated by the response time obtained when the sample concentration was increased. The water-insoluble sample can be used for effectively treating cancer in that it accelerated apoptosis of human carcinoma cells up to 70% compared to less than 50% for the control. The sample also increased the differentiation ratio of HL-60 cells up to 58% after four days of cultivation, compared to 18% in the case of no sample supplementation. These results can be used in implying that the insoluble part of G. lucidium mycelium culture broth must be related to controlling signal transduction, resulting in the regulation of cancer cell growth.