Vertical fissures (sandcracks) affect approximately 20% of adult beef cattle in western Canada. The risk factors associated with the formation of these lesions are not well understood. This paper describes a case-control study that identifies the role of increased claw size (claw volume >390 cm3, odds ratio 7.8) in the formation of the lesion. No connection was found between vertical fissures and horn hydration status. However, horn hydration was found to vary significantly between samples collected in the summer and winter, the latter samples having significantly reduced moisture content. The importance of these findings and the implications for the prevention of fissure formation are discussed.