This paper suggests definitions of three elem ents essential to successful irrigation- w ater rights, infrastructure capable of delivering the service im plied in the w ater right, and assigned operational responsibilities. D epending on w hether the basic elem ents are properly m atched, system s are defined as 'functional' or 'dysfunctional'. The im portance of interactions among these factors is illustrated through field exam ples. It is argued that perform ance analysis of dysfunctional system s is problem atic, and functionality may be a prerequisite to significant im provem ents in perform ance. The definition of water rights, particularly as undocumented and unregulated usage develops, is likely to present the most difficult challenge to achieving functionality.