Objective: To explore the domains encompassed within the assessment of the appropriateness of prescribing for an individual patient. Method: The Nominal Group Technique was used to address the question "How can we assess inappropriate drug therapy of individual patients that is responsive to pharmaceutical care?" The group participants were a self-selected group of nine pharmacists and one pharmacologist attending an international working conference on the Outcomes of Pharmaceutical Care. Item generation was followed by discussion for clarification and operationalisation. Voting achieved a consensus, defined as greater than or equal to70%, agreement on the importance of items for inclusion in an instrument to assess appropriateness. Results: Sixty-seven items were initially generated. During discussion, similar items were combined and items were grouped into domains. Items that considered the patient's perspective were commonly suggested, but many were discarded after discussing their operationalisation. Consensus was obtained that eighteen items, in seven domains, should be included in the instrument. The domains were indication and drug choice (5 items), effectiveness (2), risks and safety (2), dosage (3), interactions (1), practical use (4), and monitoring (1). Conclusion: It is hoped that, with adequate testing, these indicators of appropriateness of prescribing can be used by pharmacists to begin to routinely assess the impact of pharmaceutical care on the quality of prescribing for patients under their care.