Numerical analysis of semilinear parabolic problems Stig Larsson Lectures delivered at the EPSRC VIII-th Summer School in Numerical Analysis, University of Leicester, July 12--17, 1998. Published in ``The Graduate Student's Guide to Numerical Analysis '98'', editors M. Ainsworth, J. Levesley, and M. Marletta, SSCM volume 26, Springer-Verlag, 1999, pp. 83-117. Department of Mathematics, Chalmers University of Technology and G\"oteborg University, SE--412 96 G\"oteborg, Sweden e-mail: stig@math.chalmers.se URL: http://www.math.chalmers.se/~stig Abstract: In these lectures I discuss error analysis techniques for finite element methods for systems of reaction-diffusion equations with applications in dynamical systems theory. The emphasis is on pedagogical aspects and analysis techniques rather than on results. The list of techniques discussed include: analytic semigroup, parabolic smoothing, non-smooth data error estimate, a priori error estimate, a posteriori error estimate, exponential dichotomy, shadowing.