Based upon a thorough, quantitative investigation into the five-character poetry of the Liang *U, Chen K, and Sui Iff dynasties, this study first comes to the conclusion that, in the period in question, the tendency of "regulatedness" (lu haa HHti) basically rose day by day. With the establishment of this conclusion, two complicated problems stand out to be solved. The first is how the stress on the arrangement of the "four tones" (si sheng HS), which the Yong-ming ^RB/j movement of tonal euphony originally advocated, shifted into the arrangement of the "level and oblique tones" (ping ze ^K), which the regulated verse required. The second is how the places of tonal arrangement gradually came to be regularized as the second and the fourth characters of a line. The rest of this study provides my answer to these two problems.