Abstract
The current special issue is the indirect result of the Fourth Workshop on Graph Classes, Optimization, and Width Parameters, GROW 2009, held in Bergen, Norway, in October 2009. It is a successor to the following special issues of Discrete Applied Mathematics: 158-7 (2010) dedicated to GROW 2007, held in Eugene, Oregon; 157-12 (2009) dedicated to the second workshop in the series, held in 2005 in Prague, Czech Republic; 145-2 (2005) dedicated to the first workshop, held in 2001 in Barcelona, Spain; 54- 2/3 (1994) dedicated to a workshop, held in 1989 in Eugene, which in retrospect we view as workshop number zero in what has evolved to become the successful bi-annual GROW workshop series.