SUMMARY AND CONCLUSIONSIn this controlled randomised double‐blind parallel group study of the use of ioversol‐240 and ioversol‐320 in venography all studies were considered diagnostic with comparable quality in the two groups.Patient tolerance was high with mild heat observed in 7 patients in the ioversot‐320 group and 1 patient in the ioversol‐240 group. Assessment of pain was also comparable (2 patients in the ioversol‐240 group and 1 in the ioversol‐320 group).Both strengths of the contrast agent produced no clinically significant, drug related, changes in vital signs or laboratory parameters and there were no significant clinical adve