Bias stress effects in n-channel organic field-effect transistors(OFETs) are investigated using N,N′-bis(n-alkyl)-(1,7 and 1,6)-dicyanoperylene-3,4:9,10-bis(dicarboximide)s (PDIF-CN2) single-crystaldevices with Cytop gate dielectric, both under vacuum and in ambient. We find that the amount of bias stress is very small as compared to all (p-channel) OFETs reported in the literature. Stressing the PDIF-CN2devices by applying 80 V to the gate for up to a week results in a decrease of the source drain current of only ~1% under vacuum and ~10% in air. This remarkable stability of the devices leads to characteristic time constants τ, extracted by fitting the data with a stretched exponential—that are τ ~ 2 × 109 s in air and τ ~5 × 109 s in vacuum—approximately two orders of magnitude larger than the best values reported previously for p-channel OFETs.