This paper presents a comparative study of policy specification lan- guages. Our objective is to find policy language or notation that is the most suit- able to express the security aspects of distributed applications running on pol- icy-based networks. We first made a selection of languages and we compare them on several criteria: their suitability to specify security, their ability to ex- ress both user and network oriented security aspects, the representation tech- nique they use and the notions they are able to express. This paper concludes on a discussion on what would be the ideal policy language for distributed applica- tions that have strong security constraints.