A technique for obtaining sufficient conditions for the robust exponential stability of a parametrically uncertain system is proposed. This technique is used to study both continuousand discrete-time parametrically uncertain systems. For a common Lyapunov function we take a positive definite quadratic form that is a Lyapunov function of the system for a specific parameter value and satisfies some constraints on the first derivative (first difference). The application of our technique is illustrated by specific examples.