This paper gives necessary and sufficient conditions for the stability of time-delay systems of the form

. These new conditions are derived by Lyapunov\´s direct method through systematic construction of the corresponding "energy" function. This function is known to exist, if a solution

of the algebraic nonlinear matrix equation
![A_{2} =e^{[A_{1}+P_{1}(0)]h}P_{1}(0)](/images/tex/3824.gif)
can be determined.