OBJECTIVES: Older people (>70) with high risk of future health problems discharged from acute medical units (AMU) within 72 hours, in Nottingham and Leicester, England, were included in an RCT of an interface geriatric intervention (IGI) comprising geriatrician assessment and further specialist management. The objective was to assess cost-effectiveness of IGI compared to standard care.  METHODS: In the trial-based economic evaluation, 417 participants (IGI: 205) were analysed at 90-day follow-up. Health (inpatient, day-case, outpatient), social care and IGI resource-use data were collected and combined with unit costs to estimate total cost. Quality-adjusted life years (QALY), based on EQ-5D valuations at baseline and follow-up, were obtained for 254 (60.9%) participants. Multiple imputation by chained equations was applied to deal with missing QALY values. Cost and QALYs were adjusted by baseline characteristics using regression methods, and probabilistic incremental cost-effectiveness ratios (ICER) were constructed. Sub-group analysis was carried out for patients who had not been hospitalized within six months prior to index AMU admission.  RESULTS: In the whole group, total cost for IGI was higher (£207.4, 95%CI: £94.8-£331.2) with no QALY gain (-0.001, 95%CI: -0.009-0.007); IGI was dominated by standard care (3%-probability of ICER