The hierarchical decision procedure described by Douglas (1992) is evaluated and extended for retrofitting problems based on the experience gained from a number of industrial cases in which substantial environmentally favourable improvements have been made to processes on a one-off basis. Selected case studies (based on the publication of the Fribourg Group of German and Swiss chemical firms) are reviewed with respect to the analysis hierarchy for pollution source identification and the synthesis hierarchy for retrofit measures. The achievements of the cases are evaluated and used to refine, improve and extend the hierarchical synthesis procedure for waste minimization to process retrofitting.