The dynamic mechanical properties of some cross-linked and crystallizable polyurethanes based on polycaprolactone have been investigated with a Rheovibron Elastometer in the temperature range 150–370 K. Crystallizable samples have been studied in both quenched and annealed forms. Cold crystallization of the quenched forms occurs a few degrees above the glass temperature. Structural factors influencing both ease of crystallization and decrease in glass transition temperature are (a) decrease in cross-link density, (b) increase in MW of polycaprolactone segment, and (c) use of a flexible aliphatic diisocyanate as linking agent rather than aromatic types.