The technique of applying persistent insecticides (largely dieldrin or endosulfan) from the air by helicopter against Glossina spp. in northern Nigeria is described. In the Guinea savanna vegetation zone, a high degree of discrimination was practised. Where the riverine species G. tachinoides Westw. and G. palpalis palpalis (R.-D.) only were present, spraying was confined to the fringing forest vegetation along drainage lines and in flood plains. Where the savanna species G. morsitans submorsitans Newst. was also present, Isoberlinia woodlands were also sprayed in swaths along the outside edges and penetrating swaths at maximum intervals of 200 m; the denser vegetation encircling the many flat-topped hills was also sprayed, as well as the main tracks and cattle routes. The more undifferentiated woodlands in the southern Guinea savanna zone were sprayed as a grid with swaths at intervals of 150 to 200 m. The degree of discrimination varied according to the fly species and density of the vegetation; usually 5 to 16% of the totally infested area was actually sprayed. So far, approximately 10 000 km2 have been reclaimed from tsetse by this technique. The degree of reinvasion encountered per annum was approximately 25% of each project area. All reinfested areas have been successfully resprayed. Costs averaged approximately 18 Naira/ha actually sprayed or 2 Naira/ha of reclaimed area in the northern Guinea savanna zone. In the southern Guinea savanna zone, the reclaimed area averaged 3 Naira/ha. The ultra-low-volume spraying technique was introduced in 1972, and this has gradually replaced the conventional spraying technique using emulsion concentrates and booms and nozzles. The ULVA-Bals single-disc atomisers were modified and improved so that droplet sizes within a range of 70 to 200 μm volume median diameter can be produced as required. Many insecticides have been tested in the laboratory, preliminary tests on permethrin indicate; that it may prove to be a useful alternative to dieldrin and endosulfan.