Research on service innovation suggests that involving customers in new service development (NSD) is a major contributing factor to new service success. The objectives of this paper is to provide an overview of the literature regarding the involvement of customers in the development of new services and to offer guidelines for future research. Results show that past research has considered various antecedents and consequences of customer involvement and has also analysed various dimensions of the nature of involvement such as the intensity and modes of involvement and the communication process used to involve customers. Current research is mainly occupied with determining specific managerial practices that can lead to successful involvement of customers; the role of relationships as well as consumer motives, needs and experiences in the involvement process; the selection of customers for involvement and the effect of virtual environments. Future research should focus both on more in-depth, qualitative studies and more detailed quantitative models; analyse both buyer and seller perspectives; develop customer selection guides; formalize the involvement process; determine the role of relationship concepts in involvement and investigate how social media and brand communities can be effectively used for involving customers.