In this paper, we discuss the use of combinatorial set systems ( combinatorial designs) in the design of key predistribution schemes ( KPSs) for sensor networks. We show that the performance of a KPS can be improved by carefully choosing a certain class of set systems as key ring spaces. Especially, we analyze KPSs based on a type of combinatorial design known as a transversal design. We employ two types of transversal designs, which are represented by the set of all linear polynomials and the set of quadratic polynomials ( over some finite field), respectively. These KPSs turn out to have significant efficiency in a shared- key discovery phase without degrading connectivity and resiliency.