This paper presents the computer-aided simulation of an injection moulding process for thermoplastic materials. The reasons for using computer simulation for the injection moulding process are discussed together with description of the mould-filling and cooling phenomena. The paper also traces the difficulties in transferring the geometry of the part database from a computer-aided design environment to a computer-aided analysis environment by proposing several solutions for plastic products. Details of simulation steps will be examined by using an example part from a finite element mesh representation of mould cavity, runner and cooling channel configurations to evaluation of results from different types of analysis. Commercially available software is used for part modelling and process simulation applications.