This book constitutes the thoroughly refereed post-workshop proceedings of the 10th International Workshop on Membrane Computing, WMC 2009, held in Curtea de Arges, Romania, during August 24 to 27, 2009 under the auspices of the European Molecular Computing Consortium (EMCC) and the Molecular Computing Task Force of IEEE Computational Intelligence Society. The 22 revised full papers presented together with 10 invited papers went through two rounds of reviewing and improvement. The papers in this volume cover all the main directions of research in membrane computing, ranging from theoretical topics in mathematics and computer science to application issues; the invited lectures present fundamental contributions to membrane computing; thus highlighting important directions of current research in this area.