The death and chronic disease of the Byzantine Emperor Constantine the Monomachus is examined in the present study. Soon after his enthronement, the emperor presented with symptoms of a systemic arthritis which came in waves and left him with severe distortions and handicaps. After 12 years of continuous deterioration he developped pleural effusion with severe respiratory insufficiency. This condition led to his death few days later. A differential diagnosis of the emperor's disease is presented which concludes that it probably concerned a severe form of rheumatoid arthritis with systemic and lung involvement (possibly bilateral pleural eflusion). Lung involvement and the presence of respiratory insufficiency was the cause of Constantine the Monornachus’ death in 1055. After his death the imperial throne was left without legal succession which put an end to the glorious Macedonian dynasty. Pneumon 2000, 13 (1): 84-89