The chemical and biologic properties of a unique, new monofilament suture, polydioxanone, have been described. The inherent flexibility of its polymer allows the polydioxanone suture to be fabricated into a monofilament fiber useful for all sizes of sutures. Polydioxanone suture has greater pliability than polypropylene suture and has greater strength than that of other monofilament sutures. In the body, polydioxanone suture retains its strength for longer periods than other synthetic absorbable sutures--58 per cent versus 1 to 5 per cent at four weeks and 14 per cent versus zero per cent at eight weeks, respectively. It elicits a low order of tissue response and is absorbed by simple hydrolysis.