Objective:Our purpose was to investigate the growth regulation and postreceptor signal transduction of somatostatin (SS) on human colon cancer cell line. Methods:Low differentiated clone A cells of human carcinoma were treated with different concentrations of SS and the growth status was observed. Intracellular 1,4,5-trisphosphate (IP3) and cyclic adenosine monophosphate (cAMP) were extracted, then the concentrations of them were measured by liquid scintillation technique and gamma scintillation counter.Intracellular free calcium concentration was detected by loading Fura-2 and fluorescental technique. Protein kinase C (PKC) was extracted from cytosol and membrane, then the activity of both parts was determined with TaKai method. Results:The clone A cell growth was inhibited greatly by different concentrations of SS (10-10 to 10-5　mol/L) and it is related to the doses of SS.Somatortatin could largely inhibit the production of intracellular IP3, ［Ca2+］i, and cAMP, and decrease the activity of PKC. Conclusion:The growth of Clone A cell can be inhibited by SS. The inhibition may be mediated by phosphate inositol pathway, so intracellular IP3, ［Ca2+］i decreased, or inhibited the cell growth by inhibiting the activity of PKC.On the other hand, the cell proliferation may be inhibited by adenosine cyclase pathway, that is decreasing intracellular cAMP ,inhibiting cAMP-depending protein kinase.