Transmission electron microscopy identified adenovirus particles in 10 of 70 (14.3 per cent) samples of large intestinal content collected at postmortem examination from free-living wild red squirrels (Sciurus vulgaris) across Great Britain between 2000 and 2009. Examination was limited to cases in which an enteropathy was suspected on the basis of predetermined macroscopic criteria such as semi-solid or diarrhoeic faeces, suspected enteritis or the presence of intussusception. In most cases, meaningful histological examination of enteric tissue was not possible due to pronounced autolysis. Two (2.9 per cent) of the samples were negative for adenovirus but were found to contain rotavirus particles, a novel finding in this species.