Fowl adenoviruses (FAdVs), which belong to the genus Aviadenovirus in the Adenoviridae family, are grouped into five species named Fowl adenovirus A–E ( FAdV-A to FAdV - E ) and 12 serotypes (1–11, 8a, 8b) based on genome sequencing and virus neutralisation, respectively. FAdVs are responsible for a wide range of clinical signs, including hydropericardium-hepatitis syndrome (HHS), inclusion body hepatitis (IBH) and gizzard erosion (GE).1 HHS is primarily caused by the FAdV-4 serotype and causes more than 30 per cent mortality.2 3 IBH is related to the multiserotype of FAdVs and leads to 10–30 per cent mortality in chickens. Some FAdV-1 strains are responsible for GE.1 3 Cases of IBH or HHS have been increasing rapidly, resulting in great economic losses worldwide.3–8 In the present study, we determined the prevalence of FAdV infections in chicken flocks in China by serological analysis and characterised the genotypic distribution among the FAdV strains previously reported in China in GenBank database by phylogenetic analysis. Our findings could provide implications for a promising control measure and vaccination strategy for FAdV infection in the poultry industry. To evaluate the prevalence of FAdV infections in China, a total of 4544 serum samples were collected from 119 different non-vaccinated chicken flocks in 2014–2016. These samples were localised in 13 provinces or cities in …