This paper proposes a program for continuous estimation of respiratory mechanics parameters in ventilated patients. This program can be used with any ventilator providing airway pressure and flow signals without additional equipment. Overall breathing resistance, dynamic elastance (E) and positive end expiratory pressure (P(0)) are periodically estimated by multiple linear regression on selected parts of breathing cycles. Experimental validation together with justification of the selection procedure are based on signals obtained while ventilating a lung mechanical analogue with various intensive care ventilators. Clinical validity has been tested on 12 ventilated patients. The quality of estimation has been assessed by mean square difference between measured and reconstituted pressure (MSE), coefficient of determination (R(2)) and the condition number (a confidence index), and by comparison of E and P(0) with corresponding static values. The high R(2) and the low MSE obtained on most clinical cycles indicate that selected parts of cycles obey closely the model underlying parameter estimation. Agreement between static and dynamic parameters demonstrates the clinical validity of our program.