By means of histological, histochemical, histoenzymatic and morphometric methods terminal, respiratory bronchioles of the first, second, third order and corresponding to them in the level the branches of the pulmonary artery in the right diaphragmatic lobes were studied in 18 mature mongrel male dogs. The individually dosed physical loading the animals were given as a steady treadmill running at a speed of 15 km/h after the method developed by A. P. Sorokin, G. V. Stelnikov and A. N. Vasin (1977). Single (5 dogs) and systematic (6 dogs) loadings were given to the animals up to 3 "B" stage of the organism's adaptation. The single loading resulted in increasing energetic processes which were more manifested in myocytes of the bronchioles than in those of the arterioles. The systematic loadings resulted in hypertrophy of the spiral muscle, the elastic and reticular carcass of the bronchioles, the external elastic membranes of the arteries and the internal elastic membrane of the arteries at the levels of terminal, respiratory bronchioles of the third order.