This paper presents a test program of concrete-filled high strength steel tubular X-joints. The high strength steel tubes were cold-formed into square and rectangular hollow sections with nominal steel grades of 700 and 900 MPa. The cold-formed high strength steel tubes were infilled with normal and high strength concrete with nominal concrete grades of 35 and 100 MPa, respectively. A total of 15 tests was carried out covering chord sidewall slenderness ratios ranged from 12.6 to 40.6. In order to avoid failure of brace members and reveal the true capacity of the X-joint specimens, steel bearing plates were used to simulate the brace members. The test strengths were compared with the nominal strengths calculated using CIDECT design provisions. Overall, the nominal strengths predicted by the CIDECT design provisions are quite conservative for the concrete-filled high strength steel square and rectangular hollow section X-joints.