On April 6 1993 at 12.58 at the radiochemical plant of the Siberian Chemical Combinat (Tomsk-7), a set-up for treatment of the uranium solution prior to extraction was damaged and part of the activity was released into the environment. The release occurred through the collapsed wall and then standard ventilation system. The paper presents results obtained by Roshydromet divisions in assessing the magnitude of the accident and predicting its consequences. The meteorological data suggested that the most probable direction of the radioactive trail was north-east, towards the village of Georgievka. The preliminary sampling allowed the radionuclide composition of the release to be idenfified as 103 Ru, 106 Ru, 95 Zr, 95 Nb and 239 Pu. Based on the results of the aerial gamma survey conducted by specialists of Roshydromet and «Berezovgeologiya», an area of increased gamma background (> 10 μR/hour) was outlined. In addition, measurements were made across the radioactive trail using equipment on vehicles. The activity release was estimated on the basis of the theoretical relationship between gamma dose and isotopic activity. By calculations, 720 Ci of activity was released into the environment. The criterium of correctness was the condition of minimum deviation of the calculated gamma field from the measured one. For calculation of 239 Pu depositions, the relationship 239 Pu/ 95 Zr = (1-3.5) × 10 −3 was used. Based on data of depositions and hydrological predictions, estimates were made for possible contamination of the Samus-ka and Tom' rivers due to the surface run-off of radionuclides from the catchment area. For the village of Georgievka, respiration individual dose was calculated which may result from wind resuspension and uplift of radioactive dust containing 239 Pu. The paper also includes results of the actual aerial spectrometric gamma survey which confirm the preliminary estimates of the activity release