Isotactic polypropylene (iPP) isothermally crystallized from the melt was studied by differential scanning calorimetry (DSC) and light transmission measurements techniques. When samples crystallized isothermally above 132 degrees C, alpha-spherulites were formed only; the DSC measurements showed double melting endotherms peak. The first peak represents the melting of crosshatched lamellae in alpha-spherulites, while the second peak is correlated to melting of the radial and the reorganized tangential lamellae. Below 132 degrees C the iPP showed a broad melting peak endotherm with a melting tail endotherm at the low temperature side. The light transmission measurements showed that the tail endotherm is due to the melting of beta-spherulites and the broad melting peak is due to the melting of alpha-spherulites.