The purpose of this research is to clarify the size effect on the uni-axial compressive behavior of circular concrete-filled steel tube (CFT) short columns. Three different sizes of CFT short column specimens were tested. Other experimental , parameters were the strength of filled concrete and loading methods (applying the compression load only on the filled-concrete and on the overall cross-section). This paper first presents the test results concerning compressive strength and discusses the evaluation of the strength of circular CFT short columns considering the size and confined effects.