There is a strong association between PSC and IBD. PSC is the most common hepatobiliary lesion seen in association with IBD. Whether there are two subsets of PSC, one associated with IBD and one unassociated, is controversial. A lower male to female ratio in patients without IBD supports this view. The demonstration of the haplotype DRw52a in 100% of patients with PSC, irrespective of the absence of IBD, speaks against this view. Patients with isolated PSC tend to present with jaundice, pruritus, and fatigue more frequently than those with combined PSC and IBD. There may also be a difference in bile duct involvement between patients with and without IBD combined with PSC. Apart from usually being a total colitis, either Crohn's colitis or UC, the IBD associated with PSC cannot be distinguished from IBD without PSC with respect to symptoms and clinical course. Patients with combined IBD and PSC may have somewhat worse prognosis than those with isolated PSC. The majority of patients developing BDC have concomitant IBD, suggesting that patients without IBD represent a different subgroup of PSC and run a different clinical course. Most studies have, however, found no differences in epidemiology, pathogenetic factors, clinical findings related to the hepatobiliary disease and prognosis between those who present with PSC alone and those who present with combined PSC and IBD. A major problem when discussing the relationship between IBD and PSC is that the bowel is inadequately examined in many of the studies relating to this question.(ABSTRACT TRUNCATED AT 250 WORDS)