For the determination of CO2-content from incubation experiments infrared-absorption, interferometer and titration methods were compared with regard of the reproduction of experimental results. The data obtained by titration were general higher. The middle coefficients of variation amounted for infrared-absorption 6.79%, interferometer 13.41% and titration 21.78%. The repititions, which are necessary for the statistical safety of the methods, are given. By the method of infrared-absorption the higher water-loss of the soil is reduced by water-saturation of the air in the incubation vessel.