The prevalence and severity of adventitious bursitis and its association with age at slaughter and carcase quality were evaluated in a cohort of 1011 pigs reared in a straw.based system. The prevalence of bursitis was 85.4 per cent (574/672). Pigs with bursitis had a significantly greater depth of fat over the ribs (P=0.01) and at P2 (P=0.02). There was evidence (P=0.06) of an association between bursitis and a reduction in the depth of the rib muscle. There was also a significant reduction in the lean meat content of the carcases of the pigs with bursitis (P<0.01). There was no association with age at slaughter, sex or carcase weight. When the significant associations were considered in a forward stepwise unconditional logistic regression model, with the presence of bursitis as the dependent variable, the only significant variable was depth of rib fat with an odds ratio of 1.12 (95 per cent confidence interval 1.02 to 1.22). The economic impact of adventitious bursitis on carcase quality was estimated to be equivalent to a loss of 0.5 kg per affected pig.