[en] We have reported that ¹¹C-L-methionine (¹¹C-Met) was a useful labelled amino acid for the diagnosis of cancer using positron emission computed tomography. In this report, we studied whether ¹¹C-Met accumulated into inflammatory tissues or not for the differential diagnosis of cancer and inflammation. Aseptic inflammations on the back of Donryu rats produced by s.c. injections of croton oil or 1.5 % carrageenan, showed a low level accumulation of ¹¹C-Met as was in the muscle or blood. Time activity curves of inflammation showed clearance pattern and were significantly lower than that of pancreas, liver and cancer. Macro-autoradiographic studies ¹⁴C-Met showed the same results and hepatoma AH 109A was clearly differentiated from the inflammation induced by croton oil. It is suggested that we can differentiate cancer from inflammation with positron emission computed tomography using ¹¹C-Met. (author)