Pollens collected from Astragalus lentiginosus and Oxytropis sericea were fed to mice. At the end of the feeding period, uterine weights were taken to determine estrogenic activity, and tissue was collected for microscopic examination. The pollen from A lentiginosus, but not from O sericea, induced lesions similar to those of locoweed poisoning. The pollen from neither plant was estrogenic. Seeds from A lentiginosus produced toxicosis when fed to rats.