There are disclosed avermectin derivatives with a hydroxy and hydrocarbon substituents at the 5, 10, 13, 23, 4' and 4" positions which are prepared by the reaction of the 5, 10, 13, 23, 4' or 4" ketone compound with an organo-metallic Grignard reagent. The compounds are potent antiparasitic and anthelmintic agents in human and animal therapy and are potent pesticidical agents against agricultural pests. Compositions containing such compounds as the active agent are also disclosed.