This paper reports the analyses of cyanobacteria Microcystis spp. and toxin occurrence in bloom samples from some freshwater bodies in Vietnam. Six species of Microcystis (M. aeruginosa, M. botrys, M. panniformis, M. wessenbergii, M. flos-aquae and M. protocystis) were identified in 8 bloom samples collected from Lake Tri An (Đ ng Nai province), Lake Bien Ho and Lake Duc An (Gia Lai Province), Cua Ngan, Dap Da, Nhu Y, Ho Mung sites (Thua Thien Hue Province), Lake Hoan Kiem (Ha Noi). The results of the quantitative analyses of Microcystis spp. and screening of microcystin by ELISA in the water.