The robust stability of control systems with perturbation is considere
d. Using Lyapunov functions, quantitative bounds on the perturbation a
ve obtained such that the systems remain stable. Foul classes of pertu
rbations are treated and four measures of robust stability are propose
d: the nondelay unstructured, delayed unstructured, nondelay structure
d and delayed structured measures. Examples are given, and comparisons
with the results given in current literature are made.