Abstract: The chloroform extract and the two novel compounds streptmysone-A (I) and streptomysone-B (II) of the Czapek-Dox (alkaline) culture filtrate of the Streptomyces species were studied for cytotoxic and acute toxicity activities. The cytotoxic activity of the compounds and the extract was determined by brine shrimp lethality bioassay while the acute toxicity study was performed on Swiss albino mice. The LC₅₀ values of chloroform extract(CHCl₃), compound (I) and (II), and standard ampicillin trihydrate were found to be 3.89, 6.31, 125.8 and 6.31Fg ml^-1, respectively. The LD₅₀ values were found to be 66.34 and 79.49mg kg^-1 for the compound (1) and (II), respectively.