The development of an expert system is described for ion chromatographic methods which use ion-interaction chromatography as the separation technique. The object of the system is to help define appropriate starting conditions for the analysis of a desired group of ions. The system is implemented in a rule-based expert system development tool, Xi-Plus. Rules are used which act on certain properties of the sample and on the availability of instrumentation and accessories. With this information the method conditions can be defined for the column, detector and mobile phase. The expert system incorporates a module which allows the user to modify some of the rules in order to avoid problems which arise with expert systems which are too rigid. Many laboratories have their own preferences for columns, etc., which would be difficult for an expert system to predict. The rule change module therefore allows users to customise the system to their own requirements. Two approaches to the knowledge engineering process were employed. The first used the conventional approach of interrogation of an expert (in this case, P. R. Haddad). In the second approach, statistical analyses were applied to a previously compiled database of published ion chromatographic methods. The conclusions from these searches were then examined by the expert to define rules for the expert system. This paper describes this process of knowledge acquisition and some preliminary results on the use of the expert system.