To review the evidence for a relationship between organisational culture and health care performance. Qualitative comprehensive review: all empirical studies exploring a relationship between organisational culture (broadly defined) and health care performance (broadly defined) were identified by a comprehensive search of the literature. Study methods and results were analysed qualitatively to provide a narrative review with integrative discussion. Ten studies met the inclusion criteria. There was considerable variation in the design, study setting, quality of reporting and aspects of culture/performance considered. Four of the ten studies reviewed in detail claimed to have uncovered supportive evidence for the hypothesis that culture and performance are linked. All the other studies failed to find a link, though none provided strong evidence against the hypothesis. There is some evidence to suggest that organisational culture may be a relevant factor in health care performance, yet articulating the nature of that relationship proves difficult. Simple relationships such as 'strong culture leads to good performance' are not supported by this review. Instead, the evidence suggests a more contingent relationship, in that those aspects of performance valued within different cultures may be enhanced within organisations that exhibit those cultural traits. A striking finding is the difficulty in defining and operationalising both 'culture' and 'performance' as variables that are conceptually and practically distinct. Considerably greater methodological ingenuity will be required to unravel the relationship(s) between organisational culture(s) and performance(s). Current policy prescriptions, which seek service improvements through cultural transformation, are in need of a more secure evidential base.