The size of the normal spleen was estimated by CT in 153 children examined with indication unrelated to splenic disease. In each patient the width, thickness, length and volume of the spleen were calculated. Measurements were also normalized to the transverse diameter of the body of the first lumbar vertebra. The spleen underwent significant growth during the first 4 years of life and reached maximum size at the age of 13. There was no differences in splenic volume between boys and girls. Splenic thickness correlated best with normal splenic volume. The strongest correlation was also found between splenic thickness and volume in a group of 45 children with clinically evident splenomegaly. Splenic thickness, an easy-to-use measurement, may be employed in everyday practice to represent splenic volume on CT.