A rapid microwave method is described for staining copper in liver. This procedure was compared with a conventional method for copper. To this end, liver sections obtained from patients affected by several liver diseases associated with copper overload, were stained both with the standard rubeanic acid method for copper and with our modification of the same method, incorporating microwave treatment. Liver sections from a normal human newborn were used as a positive control. In Wilson's disease in the cirrhotic stage, copper was detected by the conventional method solely in periportal cells; following the microwave treatment, we were able to demonstrate copper in the whole lobule. In alcoholic cirrhosis, rubeanic acid stained copper only in a few periportal cells, while, by our modified method, copper was detected in almost all periportal hepatocytes. In chronic biliary tract disease, and in the newborn liver, copper was demonstrated in a few periportal cells by both the two histochemical procedures. In conclusion, although copper was detected by both procedures, a different degree of positivity was sometimes observed by using microwaves. Moreover, the microwave-treated sections showed more contrast and less artifacts. From a practical point of view, for the simplicity of employment and, above all, for its quickness (10 min), we suggest the use of our method in all conditions where copper overload is suspected.