A physiologically based extraction test (PBET) was run for the extraction of six metals (Cu, Zn, Cd, Cr, Ni and Pb) in four composts containing high concentrations of heavy metals. An aqueous solution of pepsin plus citric, acetic, and malic acids buffered to pH 2 was used to simulate the gastric mixture, and an extraction of 1h at 37 degrees C was run with a solid:liquid ratio of 1:100. The results were compared to those obtained using water and CaCl(2)-DTPA solution. The PBET extracted far more metals than water, but less than CaCl(2)-DTPA for Cu, Pb and Cr, while giving similar or slightly lower results for Cd, Zn, and Ni.