This paper presents a study that was conducted at Monash University College - Gippsland on the effect of a robot’s geometrical parameters on its dynamic performance. This research was undertaken in pursuit of an optimal dynamic performance of industrial robots. In this study an indicator was established to quantitatively measure the dynamic performance of a robot arm with respect to changes in the geometrical parameters. Since the dynamic behaviour of a robot’s arm is largely dependent on its inertia terms; the performance indicator was based on the Logarithmic function of the sensitivity of the inertia matrix’s eigenvalues to changes in a robot’s geometrical parameters. Also, since the inertia matrix is a function of the joint displacement; the performance was examined for a particular parameter over a range of joint angles. The sensitivity of the inertia matrix’s eigenvalues to changes in the non-zero parameters of an articulated robot (PUMA 560)l was examined in the course of this research. This paper presents cases related to the effect of changing the twist angles on the dynamic performance. The results of this study, which are illustrated by 3-dimensional surface plots, are discussed and analysed in this paper. All the simulation software was written in extended ANSI FORTRAN 77 and run on an HP 9000/550 computer using the UNIX operating system.