Focal changes in the spleen were rare findings in a large clinical material (less than 1% of cases). In a prospective study, which included 580 patients, lesions in the spleen were found in 40. Four focal lesions were due to infiltrates from non-Hodgkin's lymphoma. Twenty-one lesions with low echoes consisted of twelve infiltrates from Hodgkin's disease (six patients) or non-Hodgkin's lymphoma (six patients), five were due to fresh splenic infarcts and one each to an abscess, a metastasis from a carcinoma of the stomach, sarcoid and a haemorrhage. In only three of ten highly echogenic foci was a diagnosis possible (one leukaemic infiltrate and two scars following splenic infarcts). The significance of the sonographic demonstration of focal splenic lesions for diagnosis and treatment is discussed. The advantages of a sector scanner for evaluation of the spleen and splenic size are mentioned.