Clinical and pathological descriptions of inclusion body hepatitis–anaemia syndrome (IBH–AS) and hydropericardium syndrome (HpS) are presented and their causation and control are discussed. IBH–AS is a disease which has generally been thought to have a multiple aetiology, including infectious bursal disease virus, avian adenovirus and probably chicken anaemia virus. However, there is new evidence which suggests that avian adenoviruses are primary pathogens in IBH–AS. HpS is a new broiler disease which has spread throughout Pakistan. It has a number of similarities with IBH–AS. Recently, outbreaks of a disease exhibiting features of IBH–AS and HpS have been observed in North and South America. Mortality has been reported to be higher than is usual for IBH–AS and some hydropericardium has been observed.
