Polyethylene samples, crystallized from the melt both by quenching and by isothermal crystallization at each of five different temperatures, have been characterized by small-angle X-ray scattering (SAXS) to monitor the lamellar separation. The same materials were prepared for transmission electron microscopy using two different specimen preparation techniques : fixation with chlorosulfonic acid, followed by sectioning, and permanganic etching, followed by replication. Lamellar spacings were measured from negatives of micrographs obtained following specimen preparation using each of the two techniques. Measurements close to the SAXS spacings were obtained from both techniques if particular experimental procedures were followed. However, too low a value for lamellar separation was recorded when samples were fixed for insufficient time in chlorosulfonic acid, and too high a value for lamellar separation was recorded when samples were shadowed at too low an angle, following permanganic etching, or when polymer adhered to the replicas.