A comprehensive study concerning the reproducibility and stability of organic n-type field effect transistors is presented. C 60 based OFETs were chosen to investigate the fabrication reproducibility and the long term stability because C 60 is a high mobility n-type material. We fabricated 48 transistors and each transistor was measured for 24h inside the glove box. To test for life time stability – long term measurements up to three months have been undertaken. We report about the fluctuations in the device parameters of all investigated transistors by comparing the transfer characteristics, and on/off ratio for short time and long time measurements. C 60 based OFETs showed good reproducibility and stability for short time measurements and a decay for long time measurements.