A new kind of high melting (HTm) pol(l-lactide) was discovered when cyclic poly(l-lactide)s were prepared by ring-expansion polymerization with cyclic tin catalysts at 130-160 °C in bulk. By DSC measurements with 10 K min-1 melting temperatures (Tm) in the range of 190-196 °C were found. The WAXS and SAXS measurements evidenced that not a new crystal lattice but a well-ordered morphology and a higher perfection of the crystallites are responsible for the high Tm values and high crystallinities. Under identical reaction conditions SnOct2-catalyzed and alcohol-initiated ROPs do not yield these crystallites. Furthermore, it was found that the standard crystallites are kinetically favored upon rapid crystallization, whereas the high melting form of poly(l-lactide) is thermodynamically more stable.