Four forage grasses and five forage legumes were grown in greenhouse cultures containing 0.12, 0.25, 0.50, and 1.0 ppm of atrazine and of simazine in the soil. They were also planted April 2 and 9 in field plots which had been treated the previous spring with 0, 1, 2, and 4 lb/A of the same herbicides. In the greenhouse, atrazine produced more injury to the plants than simazine. In the field, residual simazine produced more marked injury. Tall fescue and alfalfa were the most tolerant crops. Timothy was the most susceptible. Red clover, Korean lespedeza, ladino clover, sweet-clover, orchardgrass, and bromegrass were intermediate.