We would be suspicious of any manufacturer of a genuine composting toilet who claimed they had never had flies in one of their composting toilets. There are a large number of dung fly species in the UK and due to their small size they can fairly easily find their way into a toilet vault. However, we are pleased to report that a recent survey of our toilets did not reveal any problems with flies. Our research has also demonstrated that should they occur the problem can be resolved by a change in the management regime. The most likely cause is due to high moisture content in the vault and this may be caused by failure to clean the urine separating system. To a large extent fly larvae will be eaten by other small predators in the compost pile. However, we cannot completely guarantee fly free performance due to the complex nature of composting processes. Dung flies are not likely to act as disease vectors because they are not usually attracted to food.