Lameness of dairy cows is a major welfare and economic problem. Degree of hardness of claws may influence chances for injury or for claw lesions, and exposure of claws to moisture may make them soft. To assess the relationship among hardness of the claw horn, quantity and rate of absorption of water, and incidence of claw lesions, 4 experiments were carried out. In the first 3 experiments, we soaked pieces of the claw horn in water for 12 to 24 h. Soaked claws gained weight and became significantly softer, indicating that water was absorbed. One-third of the total water absorbed in 24 h occurred during the first hour. Base of the abaxial and dorsal walls of the claw was harder than the sole, but became softer more rapidly when soaked in water. In the 4th experiment, significant negative correlations were detected between claw hardness of cows and severity of claw lesions, suggesting that cows with softer claws have the most severe claw lesions. Claw horn tissue absorbs water rapidly and claw hardness decreases with moisture content, suggesting that brief exposures to moist surfaces result in claws that absorb water and consequently become softer. The relationship between hardness and claw lesions indicates that cows with softer claws are at greater risk for lameness.