[en] This paper presents the status of our work on the effects of UO2 pellet shape on strains induced in Zircaloy sheaths of CANDU fuel elements. Specific aspects discussed are the effects of pellet shape on diametral, axial, and circumferential ridge strains. Possible mechanisms of circumferential ridging are considered in the light of experimental observations. Tests to optimize a pellet shape for low strains in collapsible sheathing, which were proposed or irradiated after May 1976, are discussed. (author)