Schistosomiasis still constitutes a major public health problem in some endemic parts of rural Egypt, particularly in school-aged children. The school-based health programme for schistosomiasis control adopted by the Egyptian Ministry of Health and Population (MOHP) focuses on treating enrolled schoolchildren. Children who are not enrolled or who do not attend regularly (out-of-school) do not have access to this service, in spite of evidence that the prevalence and intensity of infection are higher in these children than among children who attend school regularly. The aim of the present study was to test an intervention to extend the existing routinely applied school-based treatment to the out-of-school children. This paper reports on the costs and the coverage obtained by the intervention under 2 alternative delivery strategies: selective versus mass chemotherapy for out-of-school children. The intervention reached 885% of the out-of-school children at a relatively low cost per infected child of 2.29 L.E. (USSO.67) and 2.02 L.E. (USSO.59) for selective and mass chemotherapy, respectively. The calculations also suggest that, if the government were to implement such a programme, it would be more efficient to offer mass than selective chemotherapy at observed levels of prevalence. Sensitivity analysis showed that selective chemotherapy would be more cost-effective in areas where the prevalence of infection in out-of-school children was <43%.