Aim: To identify risk factors for early nonelective readmission in patients with chronic obstructive pulmonary disease, previously admitted for an exacerbation of their disease. Clinical characteristics were analysed with special emphasis on body weight on admission and weight changes during hospitalization. Methods: The computerized hospital database was used to select all hospital admissions in 1994 and 1995 with exacerbation of chronic obstructive pulmonary disease as main discharge diagnosis. Cases were retained if they were nonelectively readmitted within 14 days after prior discharge, and if they had no oedema. Controls were randomly selected from the discharge listing and were not readmitted within 3 months. Cases and controls were matched on several parameters including FEV1% predicted obtained during a stable phase of the disease. Hospital charts were reviewed for clinical parameters on admission, discharge and readmission. Results: Fourteen cases were retained in the study. On admission, lung function, blood gases and parameters describing morbidity and social factors, were not different in cases and controls. The discharge procedure was adequate. During hospitalization the cases lost weight (mean+/-SD) (-1.6+/-1.9 kg, P = 0.01), while controls remained weight stable. Using a matched pairs logistic regression analysis, weight loss during hospitalization (P = 0.011) and low BMI on admission (P = 0.046) were related to the increased risk of unplanned readmission. Conclusion: These findings provide further support for the concept that nutritional status is related to morbidity in COPD.