We investigated the clinical usefulness of serum laminin, type IV collagen and type III procollagen peptide (PIIIP) as markers for detection of metastasis in patients with primary or mctastatic hone and soft part tumors. The subjects consisted of 28 patients with metastatic bone tumors, 18 with primary bone tumors (benign; 10, malignant; 8), 22 with primary soft part tumors (benign; 12, malignant; 10), 18 with cancer without metastasis (as controls to metastatic bone tumor) and 60 healthy controls. Elevated levels of serum laminin, type IV collagen and PIIIP were not associated with any specific histological subtype, tumor size or location, and were clearly related to evidence of metastasis. Mean serum concentrations of laminin, type IV collagen and PIIIP were significantly higher in patients with metastasis than in patients without metastasis. Positive correlations were observed among serum laminin, type IV collagen and PIIIP levels in tumor patients. The sensitivity values for laminin, type IV collagen and PIIIP in detecting metastasis were 83.7%, 83.3% and 80.5%, respectively, with specificity of 90.0%, 86.1% and 86.1%. When two of the three markers were evaluated in identical blood samples, combined sensitivity and specificity values exhibited further increases as compared to the sensitivity and specificity of each marker. The use of all three markers led to the best combined sensitivity and specificity. These findings suggest that the combination of these markers would be a valuable screening test in predicting metastasis.