Lightweight net jackets were treated with N, N-diethyl-meta toluamide at the rate 1/8, 1/4, and 1/2 gm per gm of netting. Field studies indicated that the 1/4-gm treatment level would provide protection from mosquitoes for 6 weeks. The jackets provided protection against Culicoides furens (Poey) for over 7 weeks at the 1/4-gm treatment level. Studies with deer flies proved more variable. One jacket provided 91% protection after 2 weeks at the 1/2-gm treatment level while another failed. Through the work of several investigators, a relatively complete picture of the effectiveness of the insect repellent jacket now exists. It has been tested in a variety of countries and climates. On the basis of the data now available, we feel that the Deet-treated jacket will provide protection against a variety of blood-feeding dipterans species for at least 6 weeks.