Abstract. The value of fossil and relict soils as indicators of past climates or periods differs greatly. It is rather high when we want to reconstruct former climates, of which we can often find out the general type and partly also the approximate amount of temperature and precipitation. On the other hand reliable statements on the time which fossil soils take for their development are largely confined to relative data, which we can only get under very favourable circumstances. Absolute estimates of time can always be done only approximately. These results, however, are only useful, if the state of development of the fossil soils under discussion can be determined with sufficient reliability. Beyond all factors which influence the exactness of our statements we must keep in mind the principle, that fossil climates can only be reconstructed out of climax soils, whereas the estimation of the duration of soil development is only possible with immature soils.