Abstract The indirect determination of the water content of foods is dealt witli on the basis of tlie following general considerations: A. The absolute vapour pressure of the water in the substance to be desiccated ; B. The absolute vapour pressure of the water in the surrounding air, C. Behaviour of the non-water components of the substance to be desicented , D. Special causes of errors, viz.: 1.. Retardation in the establishment of equihbrium; 2. Retardation due to title structure of the substancc to be desiccated, 3. Crust formation; 4. Analytical errors. E. Rate of desiccation: reference methods and rapid routine methods. We prefer to consider the problems relating to the indirect determination of the water content on the basis of absolute water vapour pressures. The advantages and disadvantages of this method of treatment have been indicated.