[en] An automated system was developed for the routine preparation of carbon-11 (¹¹C) labeled radiophar-maceuticals, which consisted of three major parts including [¹¹C]methylation of the precusor with [¹¹C] iodomethane ([¹¹C]CH₃I), purification of the desired product and formulation of the final ¹¹C labeled radiopharmaceutical. The whole system included seven three-way slider valves, eleven solenoid valves, four pneumatic cylinders, a HPLC (High Performance Liquid Chromatography) system and a rotary evaporator. Using this system, we investigated the radiochemical synthesis of L-[methyl-¹¹C]methionine, which is the most widely used amino acid in tumor PET (Positron Emission Tomography) studies. The overall operation took 30-35 min including the production of [¹¹C]CH₃I (10.5 min) and decay-corrected radiochemical yield was 25%. The automated system we described herein can be widely utilized for the preparation of many ¹¹C labeled radiopharmaceuticals and has been shown to be efficient, reliable and easy to operate