Microcystins are isolated and purified by HPLC from the blue green algal (cyanobacterial) Microcysts bollom collected in Dianchi Lake of the Southwestern China. The Microcystin LR(MCYST LR), YR(MCYST YR) and RR(MCYST RR) which are diluted into three similar concentrations in advance are added to the cultured Hela and Vero tumor cells. The results after incubating for 24 hrs show: 1.all three microcystins represent toxic and inhibitory effect on the growth of the two tumor cells, furthermore, the intensity of the effect is in correspondence with the concentration of the toxins. It is almost the...