A study was performed on white rats of the physiological, biochemical, haematological and pathomorphological indices in separate and combined actions of formaldehyde (FA) (60.0 +/- 12.7 mg/m3 in one-time exposition and 7.2 +/- 1.2 mg/m3 in a 30-day long experiment) with a concomitant increased barometric pressure (IBP) characteristic of deep coal mines (111 and 123 kPa corresponding to 1000 and 2000 m deep mines respectively). It was established that, at 123 kPa, lipoid peroxide oxidation process was stimulated in combination with microcirculatory disorders, growing FA concentration in the serum and pulmanary tissues. The shifts were still more vivid at growing IBP.