Quiescent melt crystallization rates of various polyolefins including high density polyethylene (PE), isotactic form of polypropylene (PP), polybutene-1 (PB1), and poly(4-methyl pentene-1) (P4MP1) were investigated under both isothermal and nonisothermal conditions using differential scanning calorimetry (DSC). The order of overall crystallization rates under quiescent conditions from fast to slow was found to be: PE, P4MP1, PP and PB1. The Avrami equation was used to analyze isothermal and nonisothermal crystallization processes, respectively. In order to compare relative crystallization rates of these polymers, continuous cooling transformation curves for each polymer under nonisothermal condition as well as the plot of crystallization half-time as a function of crystallization temperature under isothermal conditions were constructed. Comparisons were made of the relative rate of crystallization of the different isotactic polyolefins with each other and with reports in the literature. Isotactic polyolefins with linear side groups crystallize increasingly more slowly as the side group lengthens with polypentene-1 (PPT1) and poly-hexene-1 (PHI) crystallizing even more slowly than PB1. It is notable that P4MP1, which has isobutyl as a bulky side group, and apparently poly(3-methyl butene-1) (P3MB1) showed fairly high crystallization rates. (c) 2007 Wiley Periodicals, Inc.