A series of 368 patients with hand lacerations which required suturing were randomly allocated to one of three treatment groups. The incidence of infected and of imperfectly healed wounds was noted 7 days after suturing. As well as the influence of antibiotics on healing, sixteen other factors which it was considered might affect healing were analysed. The overall infection rate was 9-8 per cent, and there was no significant difference between the three groups. The imperfect healing rate (which includes the infected cases) was 24-6 per cent. There was a lower rate (P less than 0-05) of imperfect healing in the Triplopen group (15 per cent) than in either the flucloxacillin group (29-5 per cent) or the group who received no antibiotics (29-0 per cent). Other factors associated with imperfect healing found to be significant at the 1 per cent level, were wound contamination, pain and the presence of a wet or changed dressing at the second examination.