The article analyses diurnal and seasonal rhythms of decompression disease (DD) in a group of deep-water divers during 17 years. The diurnal dynamics of DD morbidity has a straight 12 hours rhythm with acrophases between 4-8 a.m. and 4-8 p.m. The morbidity is higher at the first half of a day--from midnight till midday. Its diurnal rhythm is conditioned by circadian and ultradian rhythms of cardiorespiratory system. The seasonal DD morbidity has its maxima in September-October, February-March and May, i.e. in months of man's adaptation for changes in climate conditions. In these critical periods it is recommended to realize prolonged decompression, increasing its oxygen part, and redouble control over the health of divers.