The effect of temperature, salinity, nitrogen, culture density and depth on the growth of Gracilaria tenuistipitata were investigated between April 1985 and March 1986 in outdoor ponds in Guangxi Province,South China. The mean annual growth rate was 2.4% per day. Under favourable temperatures of 20–30 °C, daily growth rate may reach as high as 3.3%. Salinity had an obvious effect on growth and photosynthesis and growth peaked at 21%0, with a broad plateau between 7–27%0. Growth experiments showed that a total nitrogen (NH4-N plus NO3-N) concentration of 4 μM was sufficient to enable the plants to maintain a daily growth rate of 2.7%. The best growth of the plant was obtained at a culture density of 0.5-1 kg m-2 and a culture depth of 30 cm in the pond.