BACKGROUND: Over recent years increased emphasis has been given to performance monitoring of NHS hospitals, including overall number of hospital readmissions, which however are often sub-optimally adjusted for case-mix. We therefore conducted a study to examine the effect of various patient and disease factors on the risk of emergency medical readmission. METHODS: The study setting was a District General Hospital in Greater Manchester and the study period was 4.5-years. All index emergency medical admission during the study period leading to a live discharge were included in the study (n = 20,209). A multivariable proportional hazards modelling was used, based on Hospital Episodes Statistics data, to examine the influence of various baseline factors on readmission risk. Deprivation status was measured with the Townsend deprivation index score. Hazard ratios (HR) and associated 95% confidence intervals (CI) of unplanned emergency medical admission by sex, age group, admission method, diagnostic group, number of coded co-morbidities, length of stay and patient's deprivation status quartile, were calculated. RESULTS: Significant independent predictors of readmission risk at 12 months were male sex (HR 1.13, CI: 1.07-1.2), age (age >75 (HR 1.57, CI 1.45-1.7), number of coded co-morbidities (HR for >4 coded co-morbidities: 1.49 CI: 1.26-1.76), admission via GP referral (HR 0.93, CI 0.88-0.99) and primary diagnosis of heart failure (HR 1.33, CI: 1.16-1.53) and chronic obstructive pulmonary disease/asthma (HR 1.34, CI: 1.21-1.48). Higher level of deprivation was also significantly and independently associated and with increased emergency medical readmission risk at three (HR for the most deprived quartile 1.21, CI: 1.08-1.35), six (HR 1.21, CI: 1.1-1.33) and twelve months (HR 1.25, CI: 1.16-1.36). CONCLUSIONS: There is a potential for improving health and reducing demand for emergency medical admissions with more effective management of patients with heart failure and chronic obstructive airways disease/asthma. There is also a potential for improving health and reducing demand if reasons for increased readmission risk in more deprived patients are understood. The potential influence of deprivation status on readmission risk should be acknowledged, and NHS performance indicators adjustment for deprivation case-mix would be prudent.