To understand the molecular changes during ovarian cancer development, we profiled differentially expressed genes in five paired normal and cancerous ovarian tissues. Among the genes that showed differential expression, thymosin beta-10 expression was decreased in four of five cancer tissues. The decreased level of expression was confirmed by Northern. To investigate the gene's functional role in ovarian cancers, we constructed an adenovirus vector expressing thymosin beta-10 and used it to infect ovarian cancer cell lines PA-I and SKOV3. The infected cells showed disrupted F-actin stress fibers, markedly decreased cell growth, and a high rate of apoptosis. Thus, because loss of thymosin beta-10 expression may contribute to the development of a subset of ovarian cancers, restoration of thymosin beta-10 expression may be a new strategy for ovarian cancer treatment.