Electronic Journal of Differential Equations, Vol. 1998(1998), No. 24, pp. 1-10. Title: On reaction-diffusion systems Author: Luiz Augusto F. de Oliveira (Univ. de Sao Paulo, Brazil Abstract: We consider reaction-diffusion systems which are strongly coupled. we prove that they generate analytic semigroups, find a characterization for the spectrum of the generator, and present some examples. Submitted May 18, 1998. Published October 9, 1998. Math Subject Classification: 35K57, 35B35, 35B65. Key Words: reaction-diffusion systems; analytic semigroup; exponential decay; global attractor.