PSC is a progressive liver disease without effective medical treatment. There is often co-existent ulcerative colitis. Probiotics (bacterial food supplements) have been shown to benefit patients with ulcerative colitis. In the current protocol potential beneficial effects of probiotics on liver biochemistry and liver related symptoms as pruritus are being assessed in 12 PSC patients in a randomized controlled cross over study (3 months probiotics, 1 one wash-out and 3 months placebo).