The crystallinity and crystallization behavior of syndiotactic polystyrene (s-PS) alpha- and beta -crystals have been thoroughly examined using the Fourier Transform Infrared (FTIR). It is shown that absorptivity ratio of respective absorbances of "alpha -crystal/amorphous, a(alpha)" and "beta -crystal/amorphous, a(beta)" can be quantitatively determined using FTIR spectra ranging from 865 to 820 cm(-1). Results from curve fitting show that both absorptivity ratios of a(alpha) and a(beta) are 0.178 +/- 0.005 and 0.272 +/- 0.005 for alpha-and beta -crystal absorbances, respectively. The crystallization rate and crystallinity of alpha -crystal calculated from the absorptivity ratios art: higher than that of beta -crystal crystallized at 240 degreesC for the same isothermal duration in thin film sample. The formation of beta -crystal is thermodynamically more favorable while of alpha -crystal is kinetically more favorable from FTIR spectra. (C) 2001 Elsevier Science Ltd. All rights reserved.