Supplementation with vitamin E at a concentration of 25 micrograms/ml significantly increased the mean lifespan of the rotifer Asplanchna brightwelli. Of the three life stages, the prereproductive, reproductive and postreproductive, only the prereproductive stage was significantly extended by vitamin E supplementation. Vitamin E supplemented rotifers were larger than control rotifers in their early stages of life, but both groups attained the same size by the end of their lifespan.