The invention relates to novel 3-heteorcycl-1-yluracils of formula (I) wherein R?1 and R2¿ together with the interjacent nitrogen atom form an optionally substituted, optionally benzo-condensed 5-membered heterocyclic ring and R3 through R5 have the meaning given in claim 1. The invention also relates to a method of the production of these substances and to herbicidal compositions containing such compounds as active ingredients.