Total expansion of three commercial and five experimental phosphate bonded investment were tested.Total expansion was obtained by calculating setting expansion, hygroscopic expansion and thermal expansion.Followings were the results.1)The setting expansion in the mold of hydrocolloid impression was larger than that in the mold of Teflon with the numerical values being about three times to fourteen times.The investment mixed with the special liquid showed larger setting expansion than that mixed with water.2)The investment set in the mold of hydrocolloid impression and the water added investment generally showed less thermal expansion.One of them showed thermal contraction.3)Hygroscopic expansion was remarkably large in the ratio of each expansion to the total expansion, thus, the total expansion was not same.