The following results were obtained for the water properties of the 4 commercial rockwool propagation media. 1. The water retentivity of the rockwool media is excellent, because the capillary potential and porosity in the rockwool media are large. The moisture characteristics curve of the rockwool media has properties simillar to those of sandy soil. On some observations for change of volumetric water content, it was found to loose 90% of volumetric water content at a suction of 50 cm and 50% of it at a suction of 20 cm. 2. The saturated permeability ranged from 0.32 to 0.46 cm/s, and its values are affected considerably by the state and the distribution of pores in the rockwool media. The unsaturated permeability calculated by the Jackson-method varied from 10^<-12> to 10^<-1> cm/s in the range of 10 to 90% of volumetric water content. 3. The volumetric water content of the rockwool media was controlled by irrigation intensity and drainage rate at the various inclinations of the rockwool media. 4. The volumetric water content after irrigation was affected by the initial water content. It depends on the degree of porosity of the rockwool media, the geometry of rockwool fiber and the existence of entrapped air in the rockwool media.