Abstract: Apparatus having parallel-closing jaws for clamping and immobilizing ends of blood vessels to be joined together by suturing without damaging the vessel walls. A spring biasing the jaws together is adjustable to exert no more than 30 gm/cm.sup.2 in squeezing force to vessel walls in each clamp. A stay suture retainer affixed to one or more of the jaws of the apparatus receives ends of two stay sutures passed through the ends of the blood vessels to draw them together, to immobilize the vessel ends with respect to the apparatus during close, finish suturing thereof. Mayfield-type and threaded-shaft clamp pairs are disclosed, each connected to and selectively slidable along a rigid bar for adjustable spacing upon the ends of the vessels to be joined. The clamps are durable and comprise a single piece to facilitate use.