Aim. To evaluate pathomorphological changes in the lungs, myocardium and brain of experimental animals under the conditions of exposure to suspended particles (SP) of the ultrafine range of industrial aerosol. Methods. Sampling of industrial aerosol SP was carried out at the welder's workplace using a TYPHOON R-20-2 sampler using a Zaitsev absorber containing deionized water. To separate SP (≤ 100 nm), the obtained colloidal solution was filtered through a syringe with an attached filter holder with a membrane disk filter with a pore size of 100 nm. Their chemical composition was determined by the method of atomic emission spectrometry with inductively coupled plasma. The study used a model of subchronic intoxication on Wistar rats to determine the negative effect of SP. The experimental animals had being injected with ultradispersed SP in a colloidal solution intraperitoneally for 6 weeks 5 times a week at the rate of 1 ml per 100 g. body weight of the animal. Quantitative indicators of individual structural elements of internal organs were carried out using the morphometry program Videotest - Morphology 5.2.0.158.axis using an Axio Scope A1 "Carl Zeiss" microscope (Germany) with a Jenoptik Рrogres gryphax® camera of the SUBRA series (Germany). Results. It was established that the composition of ultradispersed suspended particles SP included iron, copper, nickel, molybdenum, tungsten, silicon, titanium and vanadium in various concentrations. After 6 weeks from the beginning of exposure, morphological changes in internal organs (lungs, heart, brain) did not differ from control observations. After 12 weeks from the beginning of the experiment, pathological changes were observed in all the studied organs, among which the greatest changes were observed in lung tissue. Conclusion. It was established that suspended particles of the ultrafine range, which are formed during metal welding, lead to the development of dystrophic, dyscirculatory, inflammatory, sclerotic changes in the structure of internal organs (lungs, heart, brain). The most pronounced changes in the structure of all organs were detected on the 12th week of the experiment.