A comparison of four different methods (dry combustion and three colorimetric methods) to determine organic matter content in soils was made in order to check their precision and speed. The colorimetric methods developed by Reid & Copeland (7) and by Frattini & Kalckman (4) presented the best results. They permit to handle a large number of samples in a relatively short period with high precision (coefficients of correlation were 0.998 and 0.996, respectively), as compared with the dry combustion method.