Stands of Russian knapweed (Centaurea repens L.) were reduced over 80 per cent by several combinations of crops, cultivation and herbicides. Two of the best crop rotations in a 4-year trial were: (1) a short season of intensive cultivation and a mid-August seeding of bromegrass that was sprayed with 1 lb/A of butoxyethanol ester of 2,4-dichlorophenoxyacetic acid (2,4-D) during June and 1 or 1½ lb/A during August of the second and third years. (2) Bromegrass seeded with an oat companion crop sprayed with ⅓ lb/A of 2,4-D ester the first year and annual applications of 2,4-D in June and mid-August during the second and third years. The best use of non-selective herbicides in two 2-year trials was spring application of 4 lb/A of diethylamine salt of 2,3,6-trichlorobenzoic acid (2,3,6-TBA) or 6 lb/A of diethylamine salt of polychlorobenzoic acid (PBA), plowing 10 days later, and a corn crop sprayed with ⅓ lb/A of 2,4-D ester followed by a spring-seeded oat crop sprayed with d13 lb/A of 2,4-D ester and postharvest application of 4 to 6 lb/A of 2,3,6-TBA and 6 to 8 lb/A of PBA, and plowing 10 days later. Reinfestation from established plants was not prevented, but annual application of 2,4-D prevented reinfestation from seedlings.