Investigations on two experimental farms with group-housing revealed that lameness occurred mainly at the hind legs of sows, with a higher incidence in first parity sows. The highest incidence of lameness was seen during the first 2 months of gestation and the highest prevalence in the last 2 months of gestation. No relation could be established between lameness of a sow in the last month of gestation and reproduction results. The incidence of claw lesions increased too, during the group-housing during pregnancy and was higher compared to sows kept in crates. This increase was clearest in first parity sows. In addition the observations suggest a pattern in the course of development of lesions. Claw lesions mainly occur on the outer claws of a sow. For two types of lesions left-right symmetry has been established for both the hind and the front legs. On the level of the individual animal there was no relation between the incidence of claw lesions and lameness.