This paper is concerned with detailed results of an experimental study on nonlinear dynamic stability of pitching motions of the various recovery bodies at a low subsonic speed. The experiment is conducted in an induction type transonic wind tunnel at Mach number of 0.2, and measurement of angular variation with time of the models is made for pitching oscillation with a finite amplitude. An approximate oscillation equation, that is formulated by use of an unsteady aerodynamic pitching-moment coefficient and, in general, is capable of predicting fairly accurately the experimental data having various nonlinear oscillatory modes, is proposed on the basis of the concept of a curvefitting method. It is shown that the aerodynamic pitching moment and the associated nonlinear dynamic stability can be determined from the numerical simulation to the experimental data with sufficient accuracy.