A static-renewal, 11- to 14-day toxicity test has been developed using the life cycle of the marine red alga Champia parvula (C. Ag.) Harv. It measures the vegetative growth, formation of tetrasporangia (meiosis), and formation of cystocarps (sexual fusion). The procedure has been tested with silver, copper, cadmium, lead, and cyanide. The maximum acceptable toxicant concentration (MATC) ranges were calculated for vegetative growth of females and tetrasporophytes and for production of tetrasporangia based on statistically significant differences. The MATCs were determined for sexual reproduction using the presence or absence of cystocarps to measure significance; this yielded MATC values similar to those determined by the other parameters. However, sexual reproduction was the most sensitive of the four end points examined because it dealt with absolute absence rather than statistical differences.