For the production of the clean steels, liquid steel transfer in practice from electric furnace through tundish to continuous casting mold has been studied. Samples of the slag and liquid steel were taken simultaneously from each sequential step especially including the tundish at three different times and their chemical compositions were analyzed. The metal specimens were examined under an optical microscope and the electron optics and their nonmetallic inclusions were investigated in terms of area fractions of the inclusions by an image analyzer. The results are as follows : Open stream transfers of the liquid steel from ladle to tundish and presumably from tundish to mold were found to be contributed greatly to reoxidation of metal by air. So was the reoxidation of the metal in the tundish particularly at early stage without protection by the synthetic slag. The slag carryover from the ladie to tundish towards the end of metal transfer was found to be obviously detrimental to the cleanliness of the steel.