Spinosad was evaluated against laboratory strains of the house fly, Musca domestica L. (Diptera: Muscidae) and the stable fly, Stomoxys calcitrans (L.), as well as a field isolate of the little house fly, Fannia canicularis (L.). At 0.04% and 0.08% active ingredient, spinosad exhibited poor activity against house flies on unpainted and painted plywood, but initial and 1 wk residual activities of 0.08% spinosad on sheet metal were equivalent to 0.13% permethrin. Spinosad was highly effective with rapid speed of kill against the little house fly, providing up to 42 d of residual activity on all three substrates. The initial activity of 0.08% spinosad was equivalent to 0.13% permethrin against stable flies on painted plywood and unpainted concrete blocks, with spinosad exhibiting better residual activity on concrete. Both initial and residual activities of permethrin against stable flies were superior on unpainted plywood and pre-painted metal siding, while neither compound exhibited good stable fly activity on painted concrete blocks. Stable fly reduction was >92% after 24 h exposure in rooms treated at both 0.04% and 0.08% rates, with 1 wk residual control remaining >87%. The placement of cattle that had been treated with 0.025% spinosad spray into stable fly infested rooms resulted in ≈80% control of repeated daily challenges for a period of 1 wk. Given its novel mode of action, broad spectrum and low mammalian toxicity, spinosad may be a safe and effective rotational component for the control nuisance and biting flies in and around livestock premises.