To find the mechanism for the uptake of cadmium by chlorella, cadmium distribution in chlorella cells and a chage of trace elements in chlorella were examined after addition of cadmium chloride to the medium. Precultured Chlorella ellipsoidea (C-27) was inoculated in Meyers-4N medium and bubbled with 5% CO₂ gas at 25°under illumination of 4 klx intensity. Chlorella ellipsoidea (C-27) showed an exponential growth 2 days later and reached a stational phase after 5 or 6 days. Addition of cadmium chloride (0.1 mg Cd/liter), to the medium stimulated chlorella growth and that of 1 mg/liter also stimulated the growth to the same extent as the control. With increase of cadmium concentration in the medium up to 2.5 mg/liter, a considerable inhibition of growth was observed. No change of trace elements in chlorella cells was observed when cadmium chloride was added to the medium. Over 50% of cadmium incorporated into chlorella cells was present in 105000×g supernatant, and the remaining 10-15% each in cell debris and nuclei, mitchondoria, and microsomes. Cadmium, taken up into chlorella cells, was not removed by washing out several times with 5% Na-EDTA solution but it was washed out thoroughly by 5% Na-EDTA solution if chlorella was freezedried once.