OBJECTIVES: Multimorbidity is the presence of 2 or more medical conditions. This increasingly used assessment has not been assessed in a surgical population. The objectives of this study were to assess the prevalence of multimorbidity and its association with common outcome measures.DESIGN: A cross-sectional observational study.SETTING: A UK-based multicentre study, included participants between July and October 2014.PARTICIPANTS: Consecutive emergency (non-elective) general surgical patients admitted to hospital, aged over 65 years.OUTCOME MEASURES: The outcome measures were (1) the prevalence of multimorbidity and (2) the association between multimorbidity and frailty; the rate and severity of surgery; length of hospital stay; readmission to hospital within 30 days of discharge; and death at 30 and 90 days.RESULTS: Data were collected on 413 participants aged 65-98 years (median 77 years, (IQR (70-84)). 51.6% (212/413) participants were women. Multimorbidity was present in 74% (95% CI 69.7% to 78.2%) of the population and increased with age (pCONCLUSIONS AND IMPLICATIONS: Multimorbidity is common. Nearly three-quarters of this older emergency general surgical population had 2 or more chronic medical conditions. It was strongly associated with age and frailty, and was not a barrier to surgical intervention. Multimorbidity showed no associations across a range of outcome measures, as it is currently defined. Multimorbidity should not be relied on as a useful clinical tool in guidelines or policies for older emergency surgical patients.