The ubiquitously expressed actin-binding protein, gelsolin, is known to play a role in the modulation of the actin network and in the regulation of cell growth and cell motility. In the present study, we analysed the expression of gelsolin in 241 matched cDNA pairs from human normal and tumour tissues using a Cancer Profiling Array. We found a decreased expression of gelsolin in cancer tissue from female reproductive organs, including the ovary. On a protein level, we examined the expression of gelsolin in human ovarian cancer cell lines and in a set of 110 cases of human benign and malignant ovarian tumours. Low levels of gelsolin protein were observed in four of six ovarian carcinoma cell lines, in contrast to its expression in normal ovarian surface epithelial cells. In addition, we found a reduced expression of gelsolin in borderline tumours and ovarian carcinomas compared with the epithelium of normal ovaries and benign adenomas. Decreased gelsolin expression was associated with poorly differentiated carcinomas (p=0.014). No significant association between gelsolin expression and other clinicopathological markers or patient survival could be established. In addition, we investigated the growth regulatory function of gelsolin in human ovarian cancer cell lines using cDNA transfections. Re-expression of gelsolin in OAW42 and ES-2 cells resulted in a suppression of tumour cell survival in vitro. To explore the mechanism responsible for the downregulation of gelsolin expression in ovarian carcinoma cells, we treated cells with inhibitors of DNA methylation and histone deacetylation. We observed an upregulation of gelsolin in ovarian cancer cells after treatment with both types of inhibitor. Our results suggest that gelsolin might be involved in the growth regulation of human ovarian cancer.