OBJECTIVE: To determine the feasibility of Fluids in Shock, a randomised controlled trial (RCT) of restricted fluid bolus volume (10 mL/kg) versus recommended practice (20 mL/kg). DESIGN: Nine-month pilot RCT with embedded mixed-method perspectives study. SETTING: 13 hospitals in England. PATIENTS: Children presenting to emergency departments with suspected infection and shock after 20 mL/kg fluid. INTERVENTIONS: Patients were randomly allocated (1:1) to further 10 or 20 mL/kg fluid boluses every 15 min for up to 4 hours if still in shock. MAIN OUTCOME MEASURES: These were based on progression criteria, including recruitment and retention, protocol adherence, separation, potential trial outcome measures, and parent and staff perspectives. RESULTS: Seventy-five participants were randomised; two were withdrawn. 23 (59%) of 39 in the 10 mL/kg arm and 25 (74%) of 34 in the 20 mL/kg arm required a single trial bolus before the shock resolved. 79% of boluses were delivered per protocol in the 10 mL/kg arm and 55% in the 20 mL/kg arm. The volume of study bolus fluid after 4 hours was 44% lower in the 10 mL/kg group (mean 14.5 vs 27.5 mL/kg). The Paediatric Index of Mortality-2 score was 2.1 (IQR 1.6-2.7) in the 10 mL/kg group and 2.0 (IQR 1.6-2.5) in the 20 mL/kg group. There were no deaths. Length of hospital stay, paediatric intensive care unit (PICU) admissions and PICU-free days at 30 days did not differ significantly between the groups. In the perspectives study, the trial was generally supported, although some problems with protocol adherence were described. CONCLUSIONS: Participants were not as unwell as expected. A larger trial is not feasible in its current design in the UK. TRIAL REGISTRATION NUMBER: ISRCTN 15244462.