The aim of this work is to extend the computerized method for process pre-design to encompass safety aspects. Emphasis is on the choice between different process concepts. The synthesis method is integrated into an existing computer aided process design tool. The method is based on six databanks which contain hazardous properties of chemical compounds and knowledge of safe and unsafe process concepts. The first stage of the method is a rule-based synthesis where safety rules are combined with process rules. The second step includes a safety analysis of synthetized alternatives which is done by calculating safety indices based on the safety properties of chemicals processed and the structure and conditions of the process.