Divers may experience decompression sickness (DCS). Exposure to increased ambient pressure (i.e. the pressure and time integral) as well as the decompression profile are recognized as the most important factors modulating this risk. However, a number of other "risk factors" have been suggested. One of these risk factors is multiday diving. On a theoretical basis, multiday diving may be thought to cause inert gas accumulation and such increase DCS risk during successive days of diving. This presentation will present a systematic review of animal and human studies investigating the relationship between multiday hyperbaric exposure and DCS incidence, occurrence of venous gas embolism and subjective symptoms. The vast majority of studies suggests that multiday diving will have an acclimatizing effecct, i.e. reducing DCS risk.