Following baseline CT scans, splenic subcapsular hematomas were produced in dogs by direct splenic trauma. The CT scans of the spleen were obtained one to two hours before and after administration of IV contrast media and one, two, seven, 14 and 28 days following splenic trauma. Variations in the CT image of the hematomas was correlated with time and alterations in the chemical and histologic nature of the hematoma. Initially, the hematomas were isodense with the normal spleen and identified only following IV contrast administration. The initial number of hematomas identified by CT decreased to about half after seven to 14 days and then remained stable. Analysis of the hematomas revealed an initial increase in hemoglobin which was followed by a decrease. Dry weight increased, then decreased; lipid content decreased over time; and calcium content showed no appreciable change. The CT appearance of splenic subcapsular hematomas is dependent on the age of the hematoma. CT scans done soon after trauma should be performed following administration of intravenous contrast media, while less acute hematomas should be apparent without contrast media. Changes in attenuation values of hematomas appear due to a reduction in hemoglobin content and an increase in water content of the hematoma.