The growth of Salvinia molesta has been analysed under a range of artificial and natural environmental conditions. Growth was exponential. Mean relative growth rates as high as 21.64% per day in terms of increase in number of leaves and 17.16% per day in terms of dry weight increments were recorded. Doubling times under favourable growth conditions ranged from four to ten days. Relative rates of growth were higher at higher light intensities and had an optimum at 30⚬ C. Growth is reduced at 25⚬ C and severely inhibited at 35⚬ C. The rate of growth is also adversely affected by a decrease in nutrient availability. Under natural conditions on Lake Kariba, it is considered that nutrient availability is the factor most likely to limit the rate of growth of Salvinia when other conditions are suitable for the establishment of permanent populations.