Lipoxygenase from the germ of bread wheat was purified to near homogeneity by a classical scheme. After extraction at pH 4.5 from defatted germ, lipoxygenase activity was precipitated by 40 % saturation (NH&S04 from a 25 % saturation supernatant.After dissolution in a phosphate buffer at pH 7 and extensive dialysis against this buffer, the extract was submitted to gel filtration on Ultrogel AcA 34. The final step of DEAE Sephadex A50 chromatography gave three peaks ( b , La and L3) with lipoxygenase activity. The total yield of the purification procedure was close to 307; and the degree of purification varied from 200 to 300 depending on the fraction considered. The three isoenzymes were also detected by disc electrophoresis using a specific staining method and were isolated by isoelectric focusing in a liquid medium. The molecular weight for each isoenzyme was determined to be 90 000-95 000 by gel filtration and 110 000 by electrophoresis in a gradient of acrylamide concentration. The stability, pH optimum and calcium effect have been studied. LZ and L3 were less stable than L1. Optimum pH ranged between 6-6.5 and neither isoenzyme activity was affected by calcium ions. L1 was twice as active towards j3-carotene as LZ and L3 for the same level of oxygen uptake, but in comparison to lipoxygenase from horsebean the co-oxidising power of wheat lipoxygenase was very poor.