Abstract: Tow types of the 3-roll combined pipe mill or 3RCM is described, and the advantages and the application scope thereof illustrated. Based on the STP tube-rolling technology, an overall evaluation of the KRM 4-roll planetary tube-rolling mill is made in the paper. It is pointed out that the unsuccessful running of the PSW mill, i.e., the prototype of the KRM mill is mainly due to its improper construction. The conclusion by the author is that although their significance as for the development of the tube-rolling technology as a whole couldn′t be ascertained now, the potential of the two branches of the cross-rolling elongation process is so worth paying attention by the tube-rolling sector.