The lamellar morphology in banded spherulites of poly(epsilon-caprolactone) blended with an amorphous polymer, poly(vinyl butyral), was investigated by three-dimensional transmission electron tomography. It showed a local lamellar twist on a smaller scale than the band spacing by 2 orders of magnitude. It also indicated wavy lamellae and frequent variation in the direction of the lamellar plane. All these results indicated an S-profiled lamellar structure; that is, the cross section perpendicular to the lamellar growth direction was S-shaped. S-profiled lamellae show these structures when they are sliced at a certain angle to the lamellar surface direction. Lamellar branching was also observed, but no screw dislocations that led to the formation of extinction rings were observed in this work. (c) 2007 Wiley Periodicals, Inc.