Ten gram portions of each soil sample were treated with 4 ml of solutions containing increasing amounts of inert Zn (100, 200, 400, 800 and 1,600 mg) and 0.70 mc of radioactive 65Zn. After 10 and 20 days of incubation, soluble Zn was extracted and the amount of Zn fixed was calculated by mean of the activity found in the extract and in a standard solution. The results obtained from this experiment support the following conclusions: a - in all soils studied, the amount of Zn fixed decreased from the 10th to the 20th; however, the difference was not significant; b - the quantity of Zn fixed increased as the amount of Zn applied increased.