Abstract. We describe the structure of a space-efficient phrase table for phrasebased statistical machine translation with the Moses decoder. The new phrase table can be used in-memory or be partially mapped on-disk. Compared to the standard Moses on-disk phrase table implementation a size reduction by a factor of 6 is achieved. The focus of this work lies on the source phrase index which is implemented using minimal perfect hash functions. Two methods are discussed that reduce the memory consumption of a baseline implementation