This book constitutes the thoroughly refereed post-proceedings of the 7th International Workshop on DNA-Based Computers, DNA7, held in Tampa, Florida, USA, in June 2001.The 26 revised full papers presented together with 9 poster papers were carefully reviewed and selected from 44 submissions. The papers are organized in topical sections on experimental tools, theoretical tools, probabilistic computational models, computer simulation and sequence design, algorithms, experimental solutions, nano-tech devices, biomimetic tools, new computing models, and splicing systems and membranes.