5-HT apudomas are rare. In our country, so far there has been no detailed report about using whole blood 5-HT and urinary 5-HIAA in the diagnosis of apudomas. Measurement of whole blood 5-HT in 87 and urinary 5-HIAA in 44 apudoma patients has been carried out in our laboratory since 1980. The results showed that the values of whole blood 5-HT and urinary 5-HIAA were significantly higher in apudoma patients than those in non-apudoma, postoperative apudoma and normal groups. The value of whole blood 5-HT over 130 micrograms/ml and urinary 5-HIAA over 30 mg/24 h were preliminarily recommended as diagnostic for apudomas.