Abstract: In the cultivation of Scenedesmus obliquus,the kinds of nitrogen and phosphorous compounds used in the medium have their own different effects on the growth rate and productivity of the alga.It is now clear that not only the ratio P/N in the medium has to be considered,but that the types of compounds of nitrogen and phosphorus are also very important factors.The sources of the available nitrogen and phosphorous fertilizers constitute factors of importance in high-yield cultivation of this alga. Urea.and nitrate as nitrogen sources are markedly superior to ammonium sulphate for promo- ting the growth of Scenedesmus,and calcium super-phosphate is better than phosphoric acid. A favourable growth of Scenedesmus was obtained when urea and calcium super-phosphate were used as N and P fertilizers combinedly,and gave better yields than when urea and phosphoric acid were used as the N and P fertilizers.Similar results were obtained by the use of potassium nitrate and ammonium sulphate.