Splenomegaly is commonly seen as a consequence of sedation or anesthesia, Portal hypertension, or splenic vein thrombosis. Splenic enlargement can be severe, because up to 30% of the blood volume can be pooled in the spleen. This research attempted to verify and quantify size changes associated with acepromazine splenic enlargement in cats. Radiographic images of the spleen in normal cats were collected to determine the maximum diameter in the minimum dimension prior to, and 15 min after, administration of acepromazine in cats. In this study 5 cats (DSH), 4-6 months of age and weighing 0.8 - 1.1 kg were used. Significant splenic enlargement was seen after administration of acepromazine (P<0.01). Acepromazine was injected to cats with dosage 3 mg/kg IM. These results indicate that measurable splenomegaly occurs after acepromazine administration and a condition causing measurable diffuse increased attenuation in the spleen of cats. Also, hematocrit and total serum protein (TSP) were measured before and after induction. Hematocrit decreased significantly in all cats after induction, but changes of Total protein were no significant. Correlation between decrease of hematocrit and increase of spleen size following the anesthetic protocols studied suggests sequestration of red blood cells in splenic sites. In this survey, prominence of spleen and prevention of diagnosis mistakes following prescription of tranquillizer were confirmed.