Two glutamylselenocystathionines have been isolated from the seeds of Astragalus pectinatus. These have been identified as 2-7-glutamylamino-4-(2 amino-2-carboxyethylselenyl) butyric acid and 2-amino-4-(2-7-glutamylamino-2-carboxyethylselenyl) butyric acid. The evidence for the natural occurrence of the corresponding glutamylcystathionines is also presented.