Image localized 31P magnetic resonance spectroscopy of the spleen was performed in six normal volunteers, 13 patients with splenomegaly due to haematological malignancies, and two patients with benign causes of splenomegaly. The malignant disorders had elevated phosphomonoesters (PME) compared to controls, probably due to increased turnover of membrane phospholipids, with variable alterations in high energy phosphates. There appeared to be no relationship between grade of malignancy and relative PME peak area. An overlap in spectral characteristics between the benign and malignant cases of splenomegaly existed. Serial studies in a patient with high grade lymphoma receiving combination chemotherapy showed changes in phosphorus spectra, with an increase in the phosphodiester/beta adenosine triphosphate ratio.