We consider a cellular CDMA system in which blocking is enforced when the relative interference exceeds a certain threshold level. This paper addresses a radio network design problem in such a CDMA system. Given the data of call-traffic distributed over the service area and potential sites of base stations, the objective of the problem is to locate base stations so as to minimize the associated cost for establishing base stations while keeping the probability of blocking under control. We develop an efficient algorithm for solving the design problem. Computational experiments with real-world data are conducted to show both the efficiency and the practicality of the proposed design method.