In general, standard benchmark suites are critically important for researchers to quantitatively evaluate their new ideas and algorithms. This paper proposes CHStone, a suite of benchmark programs for C-based high-level synthesis. CHStone consists of a dozen of large, easy-to-use programs written in C, which are selected from various application domains. This paper also analyzes the characteristics of the CHStone benchmark programs, which will be valuable for researchers to use CHStone for the evaluation of their new techniques. In addition, we present future challenges to be solved towards the practical high-level synthesis.