We randomised 86 patients undergoing intra-arterial cerebral digital subtraction angiography (IADSA) to receive iodixanol (Visipaque; Nycomed, Oslo, Norway) 150 mgI/ml or iohexol (Omnipaque; Nycomed) 140 mgI/ml. The efficacy and safety of these two contrast media were compared: efficacy by evaluating the diagnostic information and radiographic density yielded by the angiograms, safety by recording all discomfort connected with the injections, and all adverse events up to 24 h after the investigation. Diagnostic information was optimal in all patients and the overall radiographic density optimal in all but one (iohexol) (P = 0.49). A feeling of warmth, the only discomfort reported, was experienced by 43% and 54% of patients receiving iodixanol and iohexol, respectively (P = 0.26). Two patients in the iodixanol group and five in the iohexol group reported one adverse event (nausea, dizziness, visual disturbance or paraesthesiae) (P = 0.30); all were of mild severity except for one moderate adverse event in each group. Iodixanol 150 mgI/ml and iohexol 140 mgI/ml were demonstrated to be suitable for IADSA, with no clinically or statistically significant differences in efficacy, discomfort or adverse events.