A full recipe of a well-known Thai folkloric remedy consists of parts of five species of plants and five species of animals. This concoction has been prescribed to some cancer patients in Thailand. A previous study on anticancer activity of the extract of this Thai folkloric remedy has found that the extract could significantly inhibit tumor growth in the first 4 weeks, prolonged survival time, and increased survival rate of tumor-bearing rats. The rate of metastasis was decreased to about half in the treated group. However, in the _ vitro study against KB-cytotoxic system, the activity of this extract did not reach the standard criteria for cytotoxic activity. Thus, the extract may stimulate the activity of immune system resulting in the inhibition of cancer growth. This study was carried out in two parts. The first part was the study of the anticancer activity of the extract on serially transplanted human cervical cancer in nude mice. In this protocol, 115 nude mice were used, but after transplantation the tumor took place in only 89 mice. Finally, only 48 mice with the tumor volume of 7-16 mm(3) were recruited. They were divided into 3 equal groups having similar distribution of the tumor size. The experimental group was fed daily with the extract solution equivalent to the dose of 2580 mg/kg for 60 days. The extract solution was prepared by dissolving 2 9 of dried extract in 5 ml of sterile water. The control group was fed daily with the equivalent amount of water. The third group was injected intraperitoneally with mitomycin-c (MMC) at the dose of 1 mg/kg in day 1 and day 5 every other week. The result showed that the extract could significantly inhibit tumor growth during the 10th-60th day of treatment, in comparison with the control group (p<0.05). There was no significant difference in tumor growth inhibition between the MMC-treated group and the extract-treated group (p>0.05). MMC clearly showed statistically significant inhibition of tumor growth during the 14th-60th day of treatment, in comparison with that in the control group (p<0.05). From the standard criteria of anticancer activity, T/C must be less than 75% before the antitumor activity of the tested substance could be accepted. These criteria could be met by both the extract and the MMC beginning at 7th day and 14th day after the initiation of treatment, respectively, until the end of the experiment. All nude mice in the extract-treated group survived but in the MMC-treated group five of them died. The second part was the study of the stimulating effect of the extract on the immune response. This experiment studied the effect of the extract on natural killer cells by (51)Cr release cytotoxicity assay. The extract was fed to three groups of nude mice containing 10, 11 and 6 animals for 1,2 and 3 weeks, respectively. The results in each group were compared with those in the control group fed with sterile water with the same numbers of animals. The result showed significant increase (p<0.05) in the natural killer cell activity in the two groups fed with the extract for 1 and 2 weeks compared with the control groups. The natural killer cell activity of nude mice fed with the extract for 3 weeks was increased but did not show statistical significance when compared with the control group. The extract demonstrated no definite toxicity from a daily oral dose of 2580 mg/kg for three months in six nude mice. In conclusion, the extract~could significantly (p<0.05) inhibit the growth of cervical cancer in tumor-bearing nude mice. In addition, the extract significantly (p<0.05) affected immune response by increasing cytotoxic activity of natural killer cells against yac-1 cell (lymphoma cells) in vitro. Thus, the inhibitory effect of the extract in tumor growth may be due to the immunomodulation of the effector mechanisms, i.e. natural killer cell activity. Further study was suggested to investigate the activity of T lymphocytes and macrophages and also their efficiency in the synthesis and release of lymphokines or monokines.