In this paper, the authors consider the 'permanence' problem for two-s
pecies periodic Kolmogorov competition reaction-diffusion systems defi
ned on a bounded domain subject to Neumann boundary conditions. The ma
in result, based on comparison and maximum principle arguments, provid
es sufficient conditions for permanence and is illustrated in applicat
ion to the Lotka-Volterra competition system as well as to a general c
lass of reaction-diffusion systems. The significance of permanence in
biological systems in general is discussed.