The moisture content of wheat and barley together with the weather elements were measured at 3 different experimental sites in the Netherlands in 1990-91. The difference in the dew point temperature in the screen[house] and in the field was small. However, the differences between air temperature in the screen and those at different heights in wheat and in barley stands were considerable. In daytime the surface temperature of barley was higher than that of wheat under the same weather conditions as a result of a higher absorbtion coefficient. Both for wheat and barley, the maximum difference between the calculated moisture content was 0.5%, using the air temperature at 1.5 m height from the nearest standard weather station and the surface temperature of the spikes. Barley had a greater daily cycle in the moisture content of the grains than wheat as a result of a high equilibrium moisture content during the night and a low one in daytime.