In this study, toxicity and bioavailability of copper and zinc to Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum) were determined, with and without sediment. The freshwater green alga P. subcapitata was exposed to different copper and zinc concentrations (250-2000 mu g L-1) for 96 hours. Significant positive correlations between inhibition and toxicant concentrations as well as total cell counts and chlorophyll-a content of P. subcapitata were observed. The EC50 values indicated that P. subcapitata was more sensitive to copper and zinc with sediment, and copper was much more toxic than zinc both with and without sediment. The mean bioaccumulation (BA) increased with increasing exposure time with and without sediment. The exposure time did not significantly (p>0.05) affect the BA values without sediment. The mean BA increased with increasing metal concentration with and without sediment. The metal concentration level significantly (p<0.05) increased the BA values without sediment, and that with sediment were calculated depending on both the uptake of metals to the microalgae and adsorption of metals onto sediment particles from the water. The exposure time significantly (p<0.001) increased bioavailability of metals without sediment. The metal concentration level did not significantly (p>0.05) affect bioconcentration factor (BCF) values without sediment.