There is much emphasis on social marketing of insecticide- treated nets and some doubt whether nets provided free-of-charge will be looked after by householders. Over 5 years, questionnaires and surveys of usage and condition of nets were carried out in a town and 15 villages in north-east Tanzania, where nets and insecticide have to be purchased and in 24 other villages where over 15000 nets had been donated and annual re-treatment is provided free-of-charge. There was very high population coverage in the town but, in the villages where nets have to be purchased, only 9.3% of people used nets which were intact and/or had been insecticide-treated and could, therefore, provide protection. However, where nets had been provided free, over 90% of them were still present and were brought for annual re-treatment 3-5 years later. Thus social marketing has performed well in a town but very poorly in these villages. However, the study showed that people look after and bring for re-treatment nets which had been provided free-of-charge.