This thesis aimed to study the association between nutritional status (both undernutrition and overnutrition) and the post-stroke outcomes. In the first study, the predictive validity of a nutrition screening tool was evaluated on hospitalised elderly and stroke patients. Patients identified as being nutritionally-at-risk had a significantly increased rate of mortality and a tendency for a longer length of hospital stay, when compared to adequately nourished patients. In a second study, the association between Body Mass Index (BMI) and mortality after a first-ever stroke was explored, using data provided by the South London Stroke Register (which covers a multiethnic population of 234,533 inhabitants in South London). After adjusting for possible confounders and having the normal weight category as reference group, the risk of mortality (up to 8 years) was higher for the underweight and lower for the overweight category. In the third study, the relationship between BMI, central obesity, nutrition risk categories and outcomes at 6 months post stroke was prospectively analysed. 550 patients were recruited on admission after stroke to two London-based hospitals. The higher the BMI, and the waist circumference (WC) quartile, the lower the rate of mortality, and there were no significant associations between BMI and WC with stroke recurrence. Patients at high risk of malnutrition had significantly higher risk of mortality, length of hospital stay and hospitalisation costs. Further research is needed to determine whether nutritional support (and which type) improves patients’ outcomes. A systematic review entitled “Oral nutritional supplements (ONS) in patients at risk of malnutrition who have had a stroke” was also conducted (as part of a review of clinical guidelines on stroke care) and it was concluded that there is a lack of good quality evidence supporting the role of ONS in the management of patients at risk of malnutrition following acute stroke.