AIMS AND OBJECTIVES: To determine patient factors associated with aggressive (code grey) events in the setting of a metropolitan hospital during a six-month period, to inform screening and prevention practices. BACKGROUND: Patient aggression continues to place nurses and patients at risk. Nurses need to be able to identify situations that are likely to escalate into aggression in order to ensure their own safety and the quality of care they can provide. Research has focussed on emergency departments and psychiatric units. Approaches that are appropriate for these settings may not fit for the general inpatient setting. DESIGN: A structured audit and epidemiological analysis of hospital population, regarding incidence of aggression. METHODS: A retrospective audit of code grey event reports and medical records of patients admitted to 16 general medical-surgical wards, during a six-month period. All available records of 121 code grey events were audited. Demographic factors for patients with code grey events were compared with factors for 6472 patients admitted. Statistical tests included chi-squared, bivariate and logistic regression. RESULTS: Diagnoses associated with increased risk of code grey were the following: delirium (11 times more likely) and dementia (seven times). Patients were more likely to have a code grey event if they were over 65 years of age (more than twice), were male (more than twice), were a recipient of Veterans' Affairs pension (four times), had never been married or had been admitted through the emergency department (almost twice). CONCLUSION: This study adds to the current knowledge of the distinctive profile of patients in medical-surgical settings who are associated with aggressive events. RELEVANCE TO CLINICAL PRACTICE: It is recommended that nurses increase their focus on assessment of identified risk factors and documentation of behaviours, to help predict aggressive events, and that this focus be supported by hospital safety and care policy.