Tests have been performed at −10°C on circumferentially notched right circular cylinders of randomly oriented granular polycrystalline freshwater ice, to determine whether grain size affects fracture toughness (KIc ). Grain sizes, as measured by the linear intercept method, varied from 1.6 mm to 9.3 mm in diameter. The circumferentially notched specimen was used because of the ease with which it can be manufactured from right circular cylinders, made regularly and with considerable accuracy of alignment for some years now by workers of the Thayer School Ice Research Laboratory. A slight (25 percent) decrease in values of KIc is observed as grain size increases over the range investigated. Consideration is given to the cause of this effect and to its possible contribution to the scatter in KIc values observed by earlier workers. Other possible causes of this scatter are indicated.