A single dose of lufenuron was administered to dogs to test its efficacy in controlling cat flea (Ctenocephalides felis) infestations for at least 30 days. Efficacy measurements revealed marked differences in the reproduction capability of fleas collected from dogs in the treatment vs the control group. Essentially, all of the eggs collected from dogs treated with lufenuron were unable to develop into normal adult fleas. Conversely, in the control group, 68.6% of the flea eggs developed into normal adult progeny.