The purpose of the research reported here is to investigate the requirements of a system which will aid a designer in moving from the functional specification of a new product to a detailed Lcchnical specification of the polymer required, and to develop a system for (his purpose. A very wide range of products can be made from polymers and over 5000 polymers are commercially available. The designer usually interacts with a polymer expert and together they try to specify the polymer properties required. Over 150 parameters are involved. Once values have been assigned to these parameters existing databases can be used to identify a suitable material. Polymer experts are scarcc and there is a need for a system which wilt allow the designer to specify the parameter values dictated by the functional requirements of the design. A number of problems are identified in this area. Some of these are of a terminological and communication nature and arise from the wide range of the application areas and large numbers of parameters to be specified. Others are due to the knowledge engineering problems in fonnalising the knowledge of the polymer expert. An investigation of these problems lead to the specification of a system which combines a flexible quasi-English naLural language with a rule based paradigm. A prototype system called Advisor is built. Advisor has the unique ability of allowing the expert to create not only the rules but also the vocabulary with which these rules are constructed and with which the designer builds up a description of the application. Thus all the vocabulary used within the system is familiar to both the expert and the designer. The underlying language for the implementation of Advisor is Arity Prolog. The prototype validates the basic design decisions. Analysis of it’s performance and suggestions for further refinements and improvements are given. The prototype system which is being puL into use by a commercial plastic design company is currently being evaluated by polymer design experts in Aachcn in Germany.