Two hundred and eighty four patients undergoing laparotomy by vertical incision were randomly allocated to closure with interrupted mass sutures of No. 1 polydioxanone (PDS) or No. 1 polypropylene (Prolene). Dehiscence occurred in 0.7% of the PDS group but in 6.4% of the Prolene group (P = 0.018). Wound infection occurred in 8.6% of the PDS group and 15.4% of the Prolene group (P = 0.1). One hundred and ninety patients attended for review at a minimum of one year. Incisional herniation, usually asymptomatic, was present in 11% of each group. Knots were palpable in 2% of the PDS patients but in 12% of the Prolene: wound pain occurred in 12% of the PDS group but in 23% of the Prolene group (P = 0.06). These results suggest that PDS may be useful for abdominal closure.