This report contains the proceedings from the First International Workshop on Reengineering Towards Product Lines (R2PL) 2005, which was held on November 10th, 2005 in Pittsburgh, Pennsylvania, USA and colocated with the Working Conference on Reverse Engineering (WCRE) 2005 and WICSA 2005 the Working Institute of Electrical and Electronics Engineers/International Federation for Information Processing (IEEE/IFIP) Conference on Software Architecture. This report consists of an overview of an invited presentation, a set of position papers, and details of the workshop's outcomes.