Atomic force microscopy (AFM) was used to study the lamellar thickness and its distribution in the beta modification of isotactic polypropylene (beta-iPP) crystallized from the melt at high temperatures. Measurements were performed on lamellae oriented both flat-on and edge-on with respect to the examined surface. Average lamellar thickness was found to be dependent not only on the crystallization temperature, but also on factors such as nucleation density and isothermal lamellar thickening. The limitations and advantages of the AFM technique for evaluation of lamellar thickness are discussed.