Process safety and cost are major considerations during the design of process plant and its projected operation. It involves critical decision making for the best choice. A cost-benefit analysis is usually carried out to facilitate this activity. However the final decision rest with the engineer. In this article, a systematic procedure based on multiobjective decision analysis PROMETHEE (Preference Ranking Organization Method of Enrichment Evaluation) has been demonstrated for its usefulness through the case study of a distillation column unit. This decision analysis includes: (1) generation of alternatives for safe design, (2) analysis of alternatives based on extended HAZOP methodology for hazard identification and alternatives generation, (3) the economic module for carrying out both fixed and operating cost estimates and extended cost calculations e.g. risk cost. Aspen Plus (TM) was used to develop the computer model. The dynamic simulation of the process was carried out in Aspen Dynamics (TM) followed by The economic analysis module developed in visual basic. It has been demonstrated through the case study that significant cost savings can be achieved through prevention of incidents, injuries, loss of production, operational failures, and reduced maintenance costs. (C) 2008 American Institute of Chemical Engineers Process Saf Prog 28: 68-83, 2009