An expert system that assists the customized men's wear purchasing process is developed In the past, configuration systems have adopted either a rule- or a constraint-based representation. To overcome the limitation of the representation, an integrated representation of the Constraint and Rule Satisfaction Problems (CRSP) is adopted. Since the general purpose tool UNIK-CRSP provides concurrent, integrated and interactive reasoning, UNIK-CRSP is very suitable for assisting the personalized customer product configuration process in a natural manner Using UNIK-CRSP, the domain-specific tool UNIK-SES is developed with the additional features of candidate products selection and user interfaces. This approach should be useful for customer support in electronic marketing on the information superhighway. Copyright (C) 1996 Elsevier Science Ltd