This book constitutes the refereed proceedings of the 4thInternational Conference on Theory and Practice of Natural Computing, TPNC2015, held in Mieres, Spain, in December 2015.The 12 revised full papers presented togetherwith 20 invited talks in this book were carefully reviewed and selected from 30submissions. The scope of TPNC is rather broad, containing topics of eithertheoretical, experimental or applied interest such as soft computing, computingarchitectures, and formal models.
