The toxicity and accumulation of the heavy metals, lead (Pb) and cadmium (Cd) in a common filamentous green alga, Cladophora fracta, were studied.C. fracta were cultured in a modified Chu No. 10 medium, which was supplemented with 5, 10, 20, 40 or 80 mg/L of Pb or 0.5,1, 2, 4 or 8 mg/L of Cd, and were separately harvested after 2, 4, 6 and 8 days.The toxicity symptoms of Pb and Cd to C. fracta showed damage and reduced number of chloroplasts, disintegrated cell wall and death.There were significant decreases in the relative growth and total chlorophyll content when the exposure time and concentration were increased.The accumulation study showed that there were significant increases of metal levels in algal tissue when the exposure time and concentration were increased.The bioconcentration factor (BCF) of Pb was higher than that of Cd at the same duration, suggesting that the accumulation potential of C. fracta for Pb was higher than that for Cd.