AbstractOne thousand and sixteen insulin‐treated patients from 84 UK diabetes centres were entered into a 12‐week open study to assess the acceptability and safety of the B‐DTM(Becton Dickinson) Pen with HumulinTM(human insulin [prb], Eli Lilly&Co) cartridges. Patients completed an acceptability questionnair after six and 12 weeks' use of the Pen. Patients were asked to score various Pen characteristics on a five‐point scale of very easy to very difficult which included: changing the needle and storing and carrying the Pen; setting the insulin dose; fitting a new cartridge; injecting insulin; reading the dosage markings and noting when the cartridge was empty. Nine hundred and ten patients (90%) completed the study.The commonest insulin used was Humulin M3, a fixed mixture of 30% soluble and 70% isophane insulin (33% of patients), and the most popular dosing regimen was twice daily, (65% of patients). The average daily dose of insulin was 39 units.Three per cent of patients reported some Pen malfunction during the study, and 9% of patients at week 6 and 16% at week 12 reported Pen breakage. All aspects of Pen usage were assessed as 'very easy/fairly easy' by over 84% of patients at both week 6 and week 12; the Pen compared favourably to previous injection methods. Ninety percent of patients who previously used a needle and syringe and 62% who previously used another pen device opted to continue using the B‐D Pen at the end of