AbstractRecent experiments have supported the view that polyethylene (PE) single crystals kept in suspension, in a variety of liquids, have different physical properties compared with the same crystals after drying. The present work was undertaken in an attempt to directly measure one of the basic properties of crystals in suspension, namely their percent crystallinity (X). Differential scanning calorimetry was chosen as the primary tool for this investigation. A method has been developed to determine the weight of PE in a suspension of crystals in a nonsolvent. Thus, a determination ofXcan be made. For suspension crystals,Xwas found to be at least 88.5%, some 6% larger than that for the corresponding dried or freeze‐dried material. Implications with regard to the fold‐surface structure are discussed. Differences in degree of crystallinity as a function of drying procedure have also been obser