Approximately 100 million people are infected with Wuchereria bancrofti, a mosquito-transmitted nemotade parasite that causes deforming lymphatic filariasis in the tropics. Improved therapies and diagnostic methods have led to new thinking about lymphatic filariasis and the realization that it should be possible to interrupt transmission and eliminate the major public health problem by repeated, annual cycles of mass treatment with new single dose combination drug regimens. The Egyptian Ministry of Health is about to institute annual mass therapy with Albendazole (ALB) and diethylcarbamazine (DEC) in all filariasis endemic villages in the country with the aim of eliminating filariasis. This study comprises 4 different activities involving human subjects: These are Village studies of filariasis prevalence and intensity, school studies of antibody prevalence, A treatment trial with an assessment of infectivity of humans with mosquito feeding before and after treatment. Pre-control evaluations of villages will be performed in year 1. Mass treatment will be conducted annually by the MOH, beginning late in year one or early in year 2. Timing of annual follow-up evaluations in years 2-4 will be coordinated with the MOH so that specimens are collected at least 6 months after mass treatment but prior to the next distribution of medication. It is anticipated that the third follow-up collection will be completed by the end of year 4. A final set of follow-up specimens will be collected in year 5 if time permits. The treatment trial will compare effects of diethylcarbamzine (6 mg/kg) and albendazole (400 mg) given as a single dose, 7 consecutive daily doses, or once weekly for 4 weeks. Antibody prevalence in young children (school studies), 200-300/school; infection prevalence studies (village studies sampling humans and mosquitoes), 100 houses (approx. 500 people) per village; treatment trial, n = 60 (20 per treatment group). The project will attempt to measure effects of mass therapy with tools developed in prior studies. It is anticipated that infection prevalence rates and infection intensities will decrease following mass therapy. A successful program should lead to elimination of filariasis over time.