Oral methotrexate (MTX) is a highly effective drug for the treatment of severe psoriasis. A limitation of this treatment is its potential hepatotoxicity. In the present prospective study the value of dynamic hepatic scintigraphy (DHS) and serum aminoterminal propeptide of type III procollagen (PIIINP) were investigated as screening methods for early detection of MTX-induced hepatic damage. These relatively non-invasive procedures were compared with the liver biopsy classification, until now the gold standard to assess MTX-induced liver damage. Twenty-five MTX patients were studied. The mean cumulative MTX dose was 3.9 g (range 0.2-11.1 g). Twenty-one patients had a normal liver histology (grade I), three patients had steatosis (grade II), and one patient mild fibrosis (grade IIIA). Seven additional patients with non-MTX related hepatic cirrhosis were included as disease controls. DHS showed a clear-cut separation between the portal contribution of the MTX patients with grade I liver histology, and that of all other patients. A portal contribution larger than 52% was associated with a > 95% chance of normal liver histology. If this cut-off value had been used to postpone the liver biopsy, this would have resulted in at least a 55% reduction in the number of biopsies in patients with a normal liver histology. DHS appeared to be very promising as a screening test to differentiate between the presence or absence of MTX-induced hepatic damage, but appeared not suitable to grade the severity of hepatic damage. Although a global relationship was demonstrated between serum PIIINP concentration and hepatic damage, single measurements in individual patients were not reliable. The combination of PIIINP measurements with DHS had only a limited additional value above DHS alone. The present study indicates that DHS has great promise for the detection of early MTX-induced hepatic damage. Pending further studies, regular liver biopsies remain mandatory for the safe prolonged use of MTX in psoriasis patients.