The American house dust mite, Dermatophagoides farinae Hughes, 1961 (Acari: Pyroglyphidae), is recognized as an important source of allergens in the domestic environment. An assessment was made of the toxicity of constituents from essential oil of cade, Juniperus oxycedrus L. (Cupressaceae), and related compounds as well as four experimental spray formulations containing the oil (10–40 g/liter sprays) to adult D. farinae. In a contact + fumigant mortality bioassay, methyleugenol (24-h LC50,5.82 μg/cm2) and guaiacol (8.24 μg/cm2) were the most toxic constituents to the mites and the toxicity of these constituents and benzyl benzoate did not differ significantly.