Overseas studies that aim to quantify the evidence base of conventional medical care give varying estimates, but many of these studies have potential for bias. We do not know how much of the total healthcare Australians receive is based on the best available evidence; studies of a number of specific conditions show that there are gaps between what is known and what happens in practice. The National Institute of Clinical Studies aims to identify and test systemic approaches to embed ongoing review and uptake of evidence into routine clinical care.