ObjectiveDifferent radiologists may show considerable variation in their interpretation of renal angiograms. We therefore wished to establish the reliability of their interpretation.DesignAssessment of the intra- and inter-observer agreement of the interpretation of renal angiograms.SettingTertiary referral university hospital.PatientsHypertensive patients suspected of renovascular hypertension on clinical grounds or on the basis of renography.InterventionsPatients were prospectively selected to undergo a renal angiography via the femoral approach.Main outcome measuresIntra- and inter-observer agreement of the degree and site of stenosis.ResultsThe difference between two estimates of the degree of stenosis ranged from 0 to 65% for the individual readers and from 0 to 75% between two readers. When the site of greatest stenosis was in the origin of the renal artery, the intra-observer agreement κ ranged from 0.54–0.71, the inter-observer agreement across multiple readers being 0.43. In apost hocanalysis using two different cutoff points of stenosis (50 or 70%), the intra- and inter-observer agreement was better at the 70% cut-off-point. In a subset of patients with stenosis and a renin ratio greater than 1.5, both the intra- and inter-observer agreement were much better than when all angiograms were considered.ConclusionsAssessment of the diagnostic performance of three experienced radiologists in their interpretation of renal artery angiograms indicates that the intra- and inter- observer agreement with respect to their estimates of the degree of stenosis and the site of greatest stenosis are rather poor but their diagnostic performance improves in patients with stenosis and a renin ratio greater than 1.5. There is a need for more objective assessment of renal artery lesions.