A hypothesis-generating analysis of risk factors associated with lameness in litters was performed. The overall proportion of litters treated for lameness in 7632 litters selected from the Health and Production Surveillance system database (HEPS-database) was 12.2%. The a priori hypotheses formed was: high-risk litters are (1) large litters, (2) litters with previous diseases or deaths, (3) litters where the nursing sow had been treated, or (4) litters from high-parity sows. Litters from large conventional herds or from herds with a high stocking density were expected to have a high risk of acquiring lameness, The primary cause of lameness in litters was assumed to be joint infections. With this contagious element of disease, a considerable herd effect and thus extra-binomial variation was expected due to the dependence of litters within herds.