AbstractFor needs of planning and design, data on rainfall duration-intensity-frequency relations are necessary. For this purpose, a network of recording raingages has to be designed. Czechoslovakia has a relatively very dense network with considerably lengthy records. Analysis of this network and particularly of parameters of a new formula for rain intensity-duration-frequency relation, abstracted from this network observations, show that in conditions of a mountainous terrain, no geographical pattern related to topographical characteristics can be evaluated to limit the density of the network.On the other hand, the use of adequate statistical procedure can reduce the necessary lenght of records for the evaluation of reliable data of low frequency, which permits a rational and economical design of permanent and non-permanent networks.