Sargassum polycystum C. Ag., is an intertidal algal flora of Visakhapatnam coast. Seasonal growth behaviour was observed throughout the year in the four areas studied i.e., Jodugullapalem, Visakhapatnam, Gangavaram and Pudimadaka in the Visakhapatnam coast for two and half years (December 1995 to May 1998). Young and erect fronds are developed from the perennial holdfast in the month of March/April. Rapid increase in the mean length of erect fronds was observed from May onwards and they attain maximum size in November/December and January. Sargassum polycystum analysed from different localities and the mean length of the fronds varied slightly due to variations in the four sites. Plants of sheltered habitat, at Jodugullapalem were taller than those in more exposed habitats at Visakhapatnam and Pudimadaka. The appearance bushiness of these plants also varied in sheltered and exposed habitats. Fruiting plants with receptacles were found seasonally for 3 to 4 months from November to February in Sargassum polycystum. The percentage of fruiting plants varied during the fruiting season and maximum number of fertile plants were found in the month of December/January. Sargassum polycystum analysed from different localities and the Fruiting plants varied slightly due to variations in the four sites.