A general Jones matrix representation for an arbitrary pretilt twisted nematic (TN) cell at any given applied voltage is obtained. A simplified Jones matrix representation for the high pretilt TN cell at the field-off state is derived from this general Jones matrix representation. The validity of this simplified representation is examined by comparing the optical transmission of a high pretilt angle TN cell, at the field-off state, as a function of the cell gap thickness obtained from this simplified representation with that obtained by the general representation. The result shows that the simplified Jones matrix representation for a TN cell at the field-off state works very well even for the pretilt angle as high as 30°. In addition, a property of the average tilt angle of a TN cell is reported.