The degradation behaviour of 2,4-D and MCPA in four types of soil were determined from measurements of ¹⁴CO₂ evolution over a period of 100 days. The total ¹⁴C-organic volatile compounds evaporated from the soils during the experimental period and the residual ¹⁴C in the soils at the end of the incubation period was also determined. The degree of mineralization was different for tested pesticides, and did not exceed 30% for 2,4-D or 46% for MCPA. The greatest mineralization of 2,4-D occurred in sandy soils containing the least amount of organic carbon, while in the case of MCPA, the highest level of mineralization was observed in loamy sand and silt loam soils. Volatilization was the most important mechanism of 2,4-D loss from soils and accounted for 46.6% of the total applied dose for sandy loam soil. The emission of volatile organic substances from MCPA-treated soils was lower, with the maximum value of 10.5% being emitted from silt soil. A significant amount of the introduced radioactive material was recovered as residues. The level of ¹⁴C-extractable residues for pesticides was low and ranged from 0.9% to 4.9% of total radioactivity. However, the level of ¹⁴Cbound residues was significantly greater and ranged from 14.6% to 43.2% of total radioactivity.