This paper describes the design programs that have been evaluated for the design of Polyfelt geotextiles. The basis for the design is the design charts in the technical manual 'Polyfelt TS Design and Practice'. In addition to simply putting in figures and printing the result of the computation, this program also provides useful background information on important topics related to the use of geotextiles, such as geotextile functions, geotextile properties and specifications, useful construction hints, etc. Furthermore, even without a precise knowledge of the input parameters, a design engineer may approach the final design step by step, by providing background information for an estimation of unknown input parameters. The program was written with an expert-system language called KnowledgePro, issued by Knowledge Garden Inc., USA. Design programs are available for the following applications: road construction, hydraulic construction, drainage systems, retaining walls, and geomembrane protection.