In Uganda, the control of onchocerciasis by mass treatment with ivermectin (Mectizan) began in 1990 and has expanded greatly since 1992. The parties involved in the programme are the Uganda Ministry of Health and its National Onchocerciasis Task Force, the Mectizan Donation Programme, the African Programme for Onchocerciasis Control, a number of non-governmental development organizations and the communities where the disease is endemic. Their aim is to make the programme self-sustaining, without further outside aid, within a period of 12 years. The methodology of the ivermectin-distribution programme, based on community-directed treatment, is outlined; the constraints under which the four co-operating parties have to work are described and the effects of the social changes produced by community-directed distribution are discussed, all in terms of influence on the achievement of a programme that will be able to sustain itself without the need for outside aid.