<b>Purpose:</b> This conceptual paper will explore the application of an aspect of systems theory, the Law of Requisite Variety (LRV) to service organisations. <b>Design/methodology/approach:</b> The notion of a system has a strong history in management; in searching for theory to provide substance to service systems research the concept can provide valuable insights. Systems theory and thinking is the study of complex adaptive wholes; the focus is on the whole rather than the parts. The LRV, introduced by Ashby, concerns the behaviour of systems. The LRV states that the organisation must be able to deal with the variety introduced by the external environment, in order to remain viable. Understanding the nature of customer variety and how to deal with it is important for service organisations since variety provides both a challenge and an opportunity. This paper seeks to explore and operationalise variety in a service context. <b>Findings:</b> A new service systems model is proposed building on the LRV, systems concepts and on current developments in service classification. <b>Originality/value:</b> To further the use of systems thinking in service science and to explore how the LRV could be applied in this context. [<i>Service Science</i>, ISSN 2164-3962 (print), ISSN 2164-3970 (online), was published by Services Science Global (SSG) from 2009 to 2011 as issues under ISBN 978-1-4276-2090-3.]
