The disclosure relates to isoxazoline compounds of formula (I) wherein the variables are defined within the specification and optionally the enantiomers and geometrical isomers thereof. The disclosure also relates to their use in the control of parasites, in particular ectoparasites, in and on vertebrates. Example compounds include: N-{ 5-[5-(3,4,5-trichloro-phenyl)-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-2-methylthiophen-3-ylmethyl} -propionamide cyclopropanecarboxylic acid { 2-methyl-5-[5-(3,5-dichloro-phenyl)-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-thiophen-3-ylmethyl} -amide cyclopropanecarboxylic acid { 2-methyl-5-[5-(3,5-dichloro-phenyl)-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yl]-furan-3-ylmethyl} -amide cyclopropanecarboxylic acid { 2-methyl-5-[5-(3,4,5-trichloro-phenyl)-5-trifluoromethyl-4,5-dihydro-isoxazol-3-yf]-furan-3-ylmethyl} -amide.
