A plant life-cycle bioassay using Arabidopsis thaliana (L.) Heynh. was used to evaluate effects of several toxic chemicals. Plants were grown in vermiculite in a hydroponic system, with test chemicals added to the nutrient solution reservoir. Reduction in total biomass followed different patterns with the chemicals tested, and sensitivity increased in the order: fly ash < 2-(2-ethoxyethoxy)ethanol (DGME) < dalapon < trichloroacetic acid (TCA) < copper sulfate < bromacil < metribuzin. DGME, TCA and dalapon induced unusual morpholocial effects in which flower development was altered and pollination prevented. Reduced biomass, altered distribution of plant dry weight among vegetative, reproductive and mature seed, and morphological effects indicate that a plant life-cycle test is a valuable screening test.