Analytical modelling of subthreshold current and threshold voltage of MOS transistors 19 tested by comparison with experimental results and two-dimensional numerical calculations. For short channel devices the subthreshould current calculated according to Taylor (1978) and to the four-parameter fitting model of Poon (1973) is found to agree well with experiment. The short channel decrease of threshold voltage is also well described by Taylor. A new formula is suggested in this paper which improves the agreement with measured results. The threshold voltage of ion-implanted short-channel devices is well described by the model of Wang (1977) if the increase of the straggle duo to annealing is correctly accounted for.