Earthworms possess immunological recognition and memory as well as high regenerative abilities. Coelomic fluid was used as a source of biologically active compounds. 2. A biologically active glycolipoprotein extract from a whole earthworm tissue homogenate was isolated and named G-90. 3. G-90 forms precipitation arcs in gel with different animal and human sera. 4. It alters murine cell growth rate in vitro in serum in a dose-dependent manner and slows murine tumor growth in vivo. 5. G-90 does not contain mutagens or carcinogens.