Abstract： Objective To study the expressions of nucleostemin gene mRNA and Ki-67antigen in pituitary adenomas and investigate the role of nucleostemin gene in the tumorigenesis and development of pituitary adenomas. Methods Seventy-one samples of pituitary adenomas were collected. Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was used to detect the expression of nucleostemin gene mRNA in samples. Immunohistochemistry technique was applied to examine Ki-67 antigen expression in the paraffin sections of samples. At the same time,coherent clinical data were collected. Results Nucleostemin gene mRNA was detectable in all samples of pituitary adenomas. Between invasive and noninvasive pituitary adenomas, the difference of nucleostemin expression was extremely significant (P＜0.01), and Ki-67 labeling index (LI) was also significantly different (P＜0.05). The difference of Ki-67LI between recurrent and non-recurrent groups was significant (P＜0.05). There was a positive correlation between nucleostemin gene and Ki-67LIlevels (r=0.237, P＜0.05). Conclusions Nucleostemin gene plays an important roles in the invasion of human pituitary adenoma. Expression of nucleostemin gene is positively related to Ki-67 antigen expression, and both may be the valid clinical detection markers for assessing proliferation, invasion and recurrence of pituitary adenomas.