[(11)C]Choline has been under investigation as a PET ligand for imaging tumor tissue, especially prostate cancer. An improved, automated synthesis of the tracer now was established. [(11)C] Choline was produced by labeling 2-(dimethylamino)-ethanol (DMAE) with [(11)C]CH(3)I in a Tefzel tube at room temperature without solvent. The product was purified using a cation exchange cartridge. Reaction conditions were optimized with respect to synthesis time and amount of DMAE, resulting in radiochemical yields higher than 80% using 60 microl of DMAE in 20 min, radiochemical purity was >99% and residual DMAE was below 10 ppm. After (11)C-production of 1h at 50 microA [(11)C]choline activities of 30.0+/-5.6 GBq (n = 29) were obtained in sterile solution ready for intravenous administration.