Insect repellent compositions are provided comprising mixtures of:(a) from about 5 to about 95%, by weight, of an N-alkyl neoalkanamide having the formula: ##STR1## wherein R.sub.1 R.sub.2, and R.sub.3 are alkyl groups and the sum of the carbon atoms therein is from 6 to 12, and wherein R.sub.4 is either a hydrogen atom or an alkyl group having one to two carbon atoms, and wherein R.sub.5 is methyl, ethyl, or propyl; and(b) from about 5 to about 95%, by weight, of N,N-diethyl-meta-toluamide (DEET).Preferred repellent composition comprise mixtures of N-methyl neodecanamide (MNDA) and DEET which provide synergistic repellency effects against a variety of insects including cockroaches, silverfish, mosquitoes, flies and ants. The repellent compositions may be applied directly to surfaces to be treated or they may be incorporated in detergent compositions such as laundry detergents, floor and wall cleaners, rug cleaners and shampoos, hair shampoos and liquid and bar soaps.