Presently available techniques for rendering commonly used catheters nonthrombogenic are discussed. The desirability of such catheters is shown and the excellent protection offered demonstrated. That such catheters are able to with-stand dry storage and heat moulding is suggested, but further work in this direction will be required. The desirability of using as fine a diameter catheter as possible in any arterial work is again demonstrated. The wisdom of simultaneous bilateral femoral artery catheterization is questioned.