The serum levels of the 7S domain of type IV collagen were measured with a radio-immunoassay in 42 patients with primary biliary cirrhosis (asymptomatic: n = 28; symptomatic: n = 14), 10 patients with chronic active hepatitis, 10 patients with liver cirrhosis and 10 healthy female controls. Serum levels of the 7S domain of type IV collagen were: 4.28 ng/mL (3.88-4.72 ng/mL; mean and range of mean +/- s.d.) in healthy controls; 5.97 ng/mL (5.07-7.02 ng/mL) in patients with chronic active hepatitis; 8.23 ng/mL (6.40-10.58 ng/mL) in patients with liver cirrhosis; and 6.79 ng/mL (4.76-9.67 ng/mL) in patients with primary biliary cirrhosis. Patients with liver cirrhosis and primary biliary cirrhosis had higher levels of serum 7S domain of type IV collagen than healthy controls (P < 0.001, respectively). Serum levels of the 7S domain of type IV collagen in patients with asymptomatic primary biliary cirrhosis, 5.83 ng/mL (4.55-7.48 ng/mL) were significantly lower than those in symptomatic primary biliary cirrhosis, 9.18 ng/mL (6.53-12.91 ng/mL; P < 0.001). Serum levels of the 7S domain of type IV collagen increased significantly along with advancement of the histological stages of primary biliary cirrhosis. Serum levels of the 7S domain of type IV collagen in the paired sera of eight patients with asymptomatic primary biliary cirrhosis (mean interval 30 months, range 12-48 months) showed significant rises during the intervals (P < 0.05), while serum levels of albumin and total bilirubin did not change significantly during these intervals.(ABSTRACT TRUNCATED AT 250 WORDS)