Forty serial samples, taken at 10 cm intervals throughout the organic part of the deposit, were investigated entomologically, and considerable numbers of insects, predominantly beetles, were found. These were not evenly distributed through the deposit, but their numbers tended to form two very distinct peaks, with some evidence of a third, separated by intervals that were virtually devoid of insect remains. This spasmodic deposition of beetle fragments was attributed to periodic flooding, and this idea was given support by the habitat requirements of the insects themselves, with the greatest numbers belonging to species that live in rapidly flowing water and, in decreasing numbers, species of still water and reed beds, and species that might have been scoured from stream banks. The same faunal assemblage is repeated in each peak and there is no suggestion that the environment changed at all during the period of deposition. A number of beetle species were recorded that are no longer found living in Britain, and these, as well as the much larger number that are still native to this country, indicate a climate at least as warm as, or possibly slightly warmer than, that of the present day. Comparison with other interglacial faunas revealed no close match, but this was not surprising in view of the small number of sites so far studied. It was concluded that, although our knowledge of beetles from interglacial deposits is still inadequate to allow dating by this means, they do not contraindicate a Cromerian age for the Sugworth material and, if their evidence is taken in conjunction with that of the stratigraphy, this age seems to be the most likely.