This paper deals with the determination, of the hygroscopic equilibrium of coffee, tobacco, and vegetable seeds corresponding to relative humidities of their environment varying from 10% to 90%. Judging by the relatively low dry weights of all the samples held at 90% relative humidity, there seems to be no doubt that the high moisture content obtained for these samples were partly due to a decrease in seed dry matter. The rate of change in moisture with change in humidity differed greatly among the various kinds of seeds. Coffee and garden beans gained 0.18% in moisture with increase of 1% in humidity, while lettuce and tobacco gained half that amount.