Studies on the distribution and germination of Alexandrium sp. (A. tamarense + A. catenella) cysts in coastal areas of Southeast China showed that the cysts were only found at X1 and X2 of Xiamen Harbor, whose density was quite low (0.4 ind.g-1). In Guangxi, the cysts were found at G2 station, with a density of 2.5 ind.g-1. There were cysts at three stations at Minjiang River estuary. The density reaches maximum value at 4-6 cm sediment of M4 station, up to 6 ind.g-1. In Changjiang River estuary, the cysts distributed widely and had the largest density, up to 23.2 ind.g-1 at 8-10 cm sediment of DG-26 station. The distribution of Alexandrium sp.cysts was relevant to sediment type, sedimentation rate and current. Light had no effect on germination. With increasing temperature, germination and survival rates also increased, while the germination time decreased. Anoxia (0.01 mg O2.L-1) inhibited germination completely. Alexandrium sp. cysts could germinate throughout the year under favorable conditions.