The authors studied the electrical stability of the asymmetric fingered polysilicon thin film transistors (AF-TFTs) at different bias-stress conditions by using a new test structure with an additional contact on the n+-floating region. This structure allows to measure the two subchannel TFT (sub-TFT) electrical characteristics before and after bias stressing. The AF-TFTs show a very stable saturation regime, even when bias stressing at very high Vds, where the electrical characteristics of both sub-TFTs are degraded. The authors concluded that stability of the AF-TFTs is related to the specific operation of the device rather than to immunity of this structure to hot carrier effects.