Novel avermectin derivatives are disclosed, wherein the 5-hydroxy group is replaced by an oxime group. The avermectin-5-oximes can further be derivatized at the 4"- or 4'-positions as amino, substituted amino, acylhydrazone, semicarbazone, or substituted semicarbazone analogues. The avermectin-5-oximes are prepared by the oxidation of the 5-hydroxy compounds with manganese dioxide or with pyridinium dichromate to the known 5-oxo analogues, and these are then reacted with a hydroxylamine salt. The new compounds are potent anti-parasitic agents, in particular, the compounds are anthelmintic, insecticidal and acaricidal agents.