After the success of a controlled trial of insecticide-treated bednets in lowering child mortality, The Gambia initiated a National Insecticide Impregnated Bednet Programme (NIBP) in 1992 with the objective of introducing this form of malaria control into all large villages in The Gambia. Five areas (population 115 895) were chosen as sentinel sites for evaluation of the NIBP. During the first year of intervention a 25% reduction was achieved in all-cause mortality in children 1-9 years old living in treated villages (rate ratio 0·75 [95% Cl 0·57-0·98], p=0·04). If one area where the programme was ineffective was excluded, the reduction was 38% (0·62 [0·46-0·83), p=0·001). A decrease in rates of parasitaemia and high-density parasitaemia, an increase in mean packed-cell volume (rate ratio 0·75 [95% Cl 0·59-0·98], p=0·04) and an improvement in the nutritional status of children living in treated villages were also detected. In a country such as The Gambia, where nets were widely used and which has a good primary health care system, it is possible to achieve insecticide-treatment of bednets at a national level with a significant reduction in child mortality; but at a cost which the country cannot afford.