Background: The risk of developing long-term complications of type 1 diabetes (T1D) is related to glycaemic control and is reduced by the use of intensive insulin treatment regimens: multiple daily injections (MDI) (≥ 4) and continuous subcutaneous insulin infusion (CSII). Despite a lack of evidence that the more expensive treatment with CSII is superior to MDI, both treatments are used widely within the NHS., Objectives: (1) To compare glycaemic control during treatment with CSII and MDI and (2) to determine safety and cost-effectiveness of the treatment, and quality of life (QoL) of the patients., Design: A pragmatic, open-label randomised controlled trial with an internal pilot and 12-month follow-up with 1 : 1 web-based block randomisation stratified by age and centre., Setting: Fifteen diabetes clinics in hospitals in England and Wales., Participants: Patients aged 7 months to 15 years., Interventions: Continuous subsutaneous insulin infusion or MDI initiated within 14 days of diagnosis of T1D., Data Sources: Data were collected at baseline and at 3, 6, 9 and 12 months using paper forms and were entered centrally. Data from glucometers and CSII were downloaded. The Health Utilities Index Mark 2 was completed at each visit and the Pediatric Quality of Life Inventory (PedsQL, diabetes module) was completed at 6 and 12 months. Costs were estimated from hospital patient administration system data., Outcomes: The primary outcome was glycosylated haemoglobin (HbA 1c ) concentration at 12 months. The secondary outcomes were (1) HbA 1c concentrations of < 48 mmol/mol, (2) severe hypoglycaemia, (3) diabetic ketoacidosis (DKA), (4) T1D- or treatment-related adverse events (AEs), (5) change in body mass index and height standard deviation score, (6) insulin requirements, (7) QoL and (8) partial remission rate. The economic outcome was the incremental cost per quality-adjusted life-year (QALY) gained., Results: A total of 293 participants, with a median age of 9.8 years (minimum 0.7 years, maximum 16 years), were randomised (CSII, n = 149; MDI, n = 144) between May 2011 and January 2015. Primary outcome data were available for 97% of participants (CSII, n = 143; MDI, n = 142). At 12 months, age-adjusted least mean squares HbA 1c concentrations were comparable between groups: CSII, 60.9 mmol/mol [95% confidence interval (CI) 58.5 to 63.3 mmol/mol]; MDI, 58.5 mmol/mol (95% CI 56.1 to 60.9 mmol/mol); and the difference of CSII - MDI, 2.4 mmol/mol (95% CI -0.4 to 5.3 mmol/mol). For HbA 1c concentrations of < 48 mmol/mol (CSII, 22/143 participants; MDI, 29/142 participants), the relative risk was 0.75 (95% CI 0.46 to 1.25), and for partial remission rates (CSII, 21/86 participants; MDI, 21/64), the relative risk was 0.74 (95% CI 0.45 to 1.24). The incidences of severe hypoglycaemia (CSII, 6/144; MDI, 2/149 participants) and DKA (CSII, 2/144 participants; MDI, 0/149 participants) were low. In total, 68 AEs (14 serious) were reported during CSII treatment and 25 AEs (eight serious) were reported during MDI treatment. Growth outcomes did not differ. The reported insulin use was higher with CSII (mean difference 0.1 unit/kg/day, 95% CI 0.0 to 0.2 unit/kg/day; p = 0.01). QoL was slightly higher for those randomised to CSII. From a NHS perspective, CSII was more expensive than MDI mean total cost (£1863, 95% CI £1620 to £2137) with no additional QALY gains (-0.006 QALYs, 95% CI -0.031 to 0.018 QALYs)., Limitations: Generalisability beyond 12 months is uncertain., Conclusions: No clinical benefit of CSII over MDI was identified. CSII is not a cost-effective treatment in patients representative of the study population., Future Work: Longer-term follow-up is required to determine if clinical outcomes diverge after 1 year. A qualitative exploration of patient and professional experiences of MDI and CSII should be considered., Trial Registration: Current Controlled Trials ISRCTN29255275 and EudraCT 2010-023792-25., Funding: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment ; Vol. 22, No. 42. See the NIHR Journals Library website for further project information. The cost of insulin pumps and consumables supplied by F. Hoffman-La Roche AG (Basel, Switzerland) for the purpose of the study were subject to a 25% discount on standard NHS costs., Competing Interests: Joanne Blair undertakes paid advisory work for, and has received funding for research, to attend academic meetings and to support a nursing salary from, Novo Nordisk Ltd (Gatwick, UK), a pharmaceutical company that manufactures some of the insulins used in the SubCutaneous Insulin: Pumps or Injections? (SCIPI) study. The work undertaken by Joanne Blair for Novo Nordisk Ltd relates to growth hormone therapy and not diabetes. Mohammed Didi has received payment for advisory work and funding to attend academic meetings and to support a nursing salary from Novo Nordisk Ltd. The work undertaken by Mohammed Didi for Novo Nordisk Ltd relates to growth hormone therapy and not diabetes. Mohammed Didi has received expenses from Merck Serono Ltd (Feltham, UK) to attend educational meetings. Carrol Gamble is a member of the Efficacy and Mechanism Evaluation Programme Board of the National Institute for Health Research. Dyfrig Hughes is a member of the Health Technology Assessment (HTA) Clinical Trials Board (2010–16), the HTA Funding Teleconference (2015–16) and the Pharmaceuticals Panel (2008–12). John W Gregory reports grants from Cardiff University during the conduct of the study, and membership of the HTA Commissioning Board (2010–14). John W Gregory received speaker fees from Pfizer Inc. and Eli Lilly and Company (Basingstoke, UK), fees for attending an advisory board for Eli Lilly and Company and financial assistance to attend annual meetings of the European Society for Paediatric Endocrinology from Sanofi Genzyme (Guildford, UK), Merck Serono Ltd, Ipsen and Novo Nordisk Ltd.