A genetic algorithm (GA) approach to support interactive planning of a piping route path in plant layout design is presented. To present this approach, the paper mainly describes the basic ideas used in the methodology, which include the definition of genes to deal with pipe routes, the concept of spatial potential energy, the method of generating initial individuals for GA optimization, the zone concept in route generation using GAs, the evaluation of crossover methods, and definition and application of fitness functions. The prototype system that has been developed based on the methodology gives designers an environment to design a piping route path in an interactive and collaborative manner with a very simple operation. The GA optimization technique generates a route path through evolution of genes that represent the pipe route. A designer evaluates the route path, modifies it, conducts another GA optimization and/or repeats the procedure until the appropriate route is desig ned. The paper also presents some simulation results using the prototype system to show the validity of this approach.