The authors report a rare case of haemorrhagic pseudocyst of the spleen in a 37 years old female who had always enjoyed very good health and who didn't remember any previous chest or abdominal traumas. Due to the initial refusal of the patient to undergo splenectomy, it has been possible to follow pathology progress. An echography of the cyst 6 months later, showed a maximum diameter increase of more than 2 cm and a further thinning of the cyst wall. Afterwards the patient decided to undergo the operation. The spleen showed a hollow of 10 cm of maximum diameter, with a degraded haematic content; the final histological examination confirmed the initial diagnosis of haemorrhagic pseudocyst of the spleen.