The purpose of our study was to examine variations in normal splenic size in relation to age, gender and body habitus in vivo, and to determine normative data for splenic volume on CT. The width (W), length (L), thickness (Th), cross-sectional areas and volume (Vol) of the spleen were obtained from abdominal CT examinations of 140 patients who underwent CT for indications unrelated to splenic disease. Splenic volume did not vary significantly (-0.04 < r < 0.05, p > 0.10) with the patient's age, gender, height, weight, body mass index or the diameter of the first lumbar vertebra, the latter considered as representative of body habitus on CT. The mean value of the measured splenic volume (S Vol) was 214.6 cm3 with a range from 107.2 to 314.5 cm3. S Vol correlated well with all the linear and the maximal cross-sectional area measurements and could be calculated using the formula: S Vol = 30 + 0.58 (W x L x Th.). Employing the same formula splenic volume was reliably assessed in 47 patients with clinically evident splenomegaly. Quantitative assessment of splenic volume might be of value in assessing mild variations in splenic size, because splenomegaly is the most common manifestation of splenic involvement in many disorders.