Summary This paper is an exploratory study of the nature of uncertainty and its connection to communication practices in supply chain relationshi ps, based on a series of case studies of relationships in the electronics/information techno logy industry. The authors interviewed both buyers and suppliers in six relationships, as part of a wider study on communication channels in supply chain relationships. Concepts of uncertaint y and ambiguity are examined through their effect on the choice of communication methods. The authors conclude that the two concepts merit separate examination, and that further work i s needed to operationalise ambiguity. There were also indications that ambiguity is higher in s ervice-oriented relationships, and in particular in service relationships that are not electronicall y mediated.