Tumor-associated glycoprotein (TAG) 72 is a mucin-like protein of high molecular weight (220-400 kd). Elevated serum levels of TAG72 are preferentially observed in patients suffering from gastric cancer. Additionally the determination of TAG72 may be a helpful tool in the management of patients suffering from mucinous ovarian cancer, in whom the clinical sensitivity of CA125 is low. The new Elecsys CA72-4 assay-available as Elecsys 2010 and 1010--was evaluated in a first field study. The test has a wide measuring range (300 U/ml) and low detection limit (0.5 U/ml) which favours its routine use. Typical precision values are 2% for intra-assay, 4% for inter-assay and 6% for inter-instrument-precision. Method comparisons to Enzymun-Test CA72-4 showed a correlation between 0.91 and 0.96. The correlation to a commercially available RIA was 0.8. With human ascites material no Hook-effect was observed up to 20,000 U/ml. No Hama-interference with clinically relevant HAMA-samples was detected.