A new preparation of amethocaine in the form of a self-adhesive patch, designed to provide topical cutaneous anaesthesia prior to venous cannulation, was evaluated in an open study of 189 children. The new preparation of amethocaine was in place for a mean time of 48 min (SD 3.9). Eighty percent of patients had a satisfactory degree of analgesia for venous cannulation. Nine percent of patients experienced moderate pain and 11% experienced severe pain during venous cannulation. In 26% of patients there was slight (24%) or moderate (2%) erythema at the site of application, and in 5% slight oedema was noted at the site of application. Eight percent of patients had slight itching and 1% had moderate itching at the site of application. There was a clinical impression that venous dilatation made cannulation easier than with EMLA cream. These results suggest that this convenient preparation of amethocaine is highly effective at providing adequate topical cutaneous anaesthesia with a short onset time and a low incidence of minor side effects with no evidence of systemic toxicity.