A study of mineralization of 14C atrazine (6-chorine-N-ethyl-N' -(1methyl ethyl) 1,3,5 triazine-2,4-diamine) was developed in three soils of different characteristic s coming one of them from Mosquera, Cundinamarca (Clay loam) and two of Saldana, Tolima (Silty loam and Sandy loam). Technical and radiolabed atrazine (specific activity 47,756 μ Ci/mg) mixturewas applied to soil samples in adose of 2.0 kg/ha. Results showed different behavior of the mineralization of the herbicide for each soil at the end of 17 weeks. The highest mineralization percentage, 15 %, was registered in the soil with higher organic matter content (12.1 %) and was the one coming from Mosquera, Cundinamarca. It was evaluated the bound and methanol extractable 14C in the fifth, nineth an seventeenth weeks and also it was analyzed atrazine and its metabolites in the extracts by thin layer chromatography. The extraction data revealed that the majority of the 14C was bound to the soil (62-83 %) and the minor fraction was methanol extractable in all the three soils. The analysis showed that the 14Cin all soils was present as atrazine and hydroxyatrazine. In the Sandy loam soil was observed the highest degradation of atrazine to hidroxyatrazine that it is not produced by biological process. It was not detectable other atrazine metabolites.