In submicrometre-sized metal-oxide-semiconductor field-effect transistors, MOSFETs, the alternate capture and emission of carriers at individual Si-SiO2 interface defects generates discrete switching in the source-drain resistance. The resistance changes are observed in the drain current as random telegraph signals (RTSs) or as stepped transients after a strong perturbation of the trap occupation. The study of individual defects in MOSFETs has provided a powerful means of investigating the capture and emission kinetics of interface traps, it has demonstrated the defect origins of low-frequency (1/f) noise in MOSFETs, and it has provided new insight into the nature of defects at the Si-SiO2 interface. The analysis of individual interface defects has shown that a Coulomb energy of several hundred millivolts is involved in the transfer and localization of the single charge carrier into the interface trap.