Abstract: The present invention provides a stable composition which comprises a non-hydroxyl-group-containing solvent mixture comprising N,N-diethyl-m-toluamide and ?-hexalactone, optionally with dimethyl sulfoxide, eucalyptol and 1-methoxy-2-propyl acetate; and an effective amount of each of amitraz and at least one additional parasiticidal compound, such as R-28153. Said composition allows for high concentrations of a mixture of parasiticidal agents in a single application and is useful for treating and controlling parasiticidal infection and infestation in a homeothermic animal.