In this study we attempted to determine the diagnostic accuracy and reproducibility of ultrasonography (US) for jaundice and to see how US can best be combined with preliminary clinical-biochemical diagnoses to plan the invasive work-up. US proved reproducible in two diagnostic departments (127 agreements in 135 cases). But, since obstruction was underdiagnosed (15 double-false negatives), the predictive value of a negative result was only 0.83. By adding a term which represents the US conclusion, obstruction or not, to the Copenhagen pocket diagnostic chart score (based on the logistic model) we found that an obstructive conclusion increases the odds of obstruction by a factor of 25, and a non-obstructive conclusion decreases the odds by a factor of only 1.9. We conclude that the preliminary diagnosis is frequently sufficiently certain to be unalterable by US. This leaves only 40% of the jaundice cases in which US is necessary to plan invasive work-up. The US workload can even, it appears, be reduced to about 22% without appreciable penalty in terms of unrewarding invasive procedures. Using these strict indications, four US examinations seem to suffice to avoid one such error. Relying on either US or clinical-biochemical data alone is inferior to the combined strategy.