Objective: To describe the patterns of single and multiple helminth infection in school children from Busia District, Kenya.

Design: A cross-sectional school survey using a randomly selected sample, forming part of an evaluation study of an ongoing deworming project.

Setting: Budalangi and Funyula divisions of Busia District, Western Province, Kenya.

Subjects: One thousand seven hundred and thirty eight school children aged 8-20 years randomly selected from those enrolled in standards 3-8 in 25 randomly selected primary schools.

Results: Overall, 91.7% of children were infected with either hookworm, Ascaris lumbricoides, Trichuris trichiura or Schistosoma mansoni. Infection prevalence of each species varied considerably among schools, being most marked for S. mansoni, where prevalence was highest in lakeshore schools. Children were typically infected with two or more species of helminth. Infection intensity of each geohelminth species was higher in school children infected with multiple species than in school children with single species infections, and intensity increased with the number of concurrent infections.

Conclusion: Helminth infections are exceptionally common among school children in Busia district, thus confirming the good sense of the school-based approach adopted by the control programme. The study also shows that there is an association between concurrent infection