Purpose - The purpose of this paper is to examine how and why business firms, both as suppliers and as customers, make specific adaptations to their products and processes to meet the particular requirements of another firm with which they are transacting business. Design/methodology/approach - The paper is based on qualitative interviews with key decision makers in international services business-tobusiness organisations. Findings - The results show that adaptations cover many areas within a company, and that the explicit costs and benefits of adaptations were calculated only to a limited extent. The paper shows that most of the suppliers investigated make adaptations to meet market and customer requirements, whereas customers make adaptations following an explicit relationship management approach. Research limitations/implications - Specific adaptation by one firm for another in the context of long-term buyer-seller relationships is an everyday fact of life and clearly of importance to the understanding of business marketing strategy. This aspect of business-to-business marketing deserves greater research attention. Practical implications - Managers often have a narrow view of adaptation as the alteration of tangible factors, in particular the product or the production process. By taking a broader view of adaptations - to include personnel/human resources, behavioural and organisational structure changes - managers would open up a wider repertoire of strategies for relationship management, to the benefit of their firms. Originality/value - Although adaptations are important for competitive success in business-to-business markets, the main types of adaptations, their costs and benefits, and the motivation of companies to make adaptations, have been subject to relatively little research, a gap, which this paper seeks to address.