In this paper we present the radiochemical synthesis of the novel compound [N-methyl-C-11]methylene blue. The synthesis of [N-methyl-C-11]methylene blue was accomplished by means of C-11-methylation of commercially available Azure B using [C-11]methyl trifluoromethanesulfonate ([C-11]methyl triflate). Following purification [N-methyl-C-11]methylene blue was obtained with a radiochemical purity greater than 97% in a 4-6% decay corrected radiochemical yield. The synthesis was completed in an average of 35min following the end of bombardment. Copyright (C) 2003 John Wiley Sons, Ltd.