Early emergency readmissions is a common and important problem in the elderly patient. Identification of the risk factors for early emergency readmissions is needed to prevent this occurring. The aim of this study was to study the risk factors for early emergency readmission in the elderly medical patient. A case-control study (sex- and age-matched) was conducted from March to December 1996. 380 elderly (age 65 years or over) medical patients with emergency hospital readmission (within 28 days) and 380 matched controls were recruited from an acute university general hospital in Hong Kong. Potential risk factors which included demographic, socio-economic, principal medical diseases, comorbid diseases, dysphagia, physical functional status and mental status were studied. In bivariate analyses for the risk factors of early emergency readmission, institutional caregiver, previous visiting nurse service, adverse drug reaction, chronic obstructive pulmonary disease, end-stage renal failure, mobility being chair- or bed-bound, dysphagia, use of a nasogastric tube feeding, urinary incontinence and bowel incontinence were significant. Readmission cases had higher mean number of comorbid diseases, lower mean Barthel Index, higher mean number of impairments in Activities of Daily Living (ADL) tasks and lower mean Abbreviated Mental Test score than controls. In multivariate logistic regression model, the number of ADL impairments (OR = 1.13, 95% CI = 1.08-1.19), no income (OR = 2. 28, 95% CI = 1.19-4.37), adverse drug reaction (OR = 4.19, 95% CI = 1.56-11.2), advanced malignancy (OR = 2.45, 95% CI = 1.37-4.37), congestive heart failure (OR = 1.63, 95% CI = 1.05-2.53), chronic obstructive airways disease (OR = 2.1, 95% CI = 1.47-3.02), end-stage renal failure (OR = 5.48, 95% CI = 1.69-17.75), dysphagia (OR = 3.9, 95% CI = 1.5-10.11) and the number of comorbid diseases (OR = 1.3, 95% CI = 1.13-1.49) were significant risk factors for early emergency readmissions. Living in a private old aged home was associated with a lower risk of readmissions (OR = 0.53, 95% CI = 0. 36-0.93). Definite medical, functional and socio-economic factors were found to be risk factors for early emergency readmissions in the elderly medical patient. A multiple risk factors intervention approach should be considered in designing future prevention strategies.