Recent studies suggest that pre-eclampsia is associated with a Th1 predominant state and may be considered a failure of tolerance. Granulysin is a cytotoxic granule protein of natural killer (NK) cells and cytotoxic T lymphocytes (CTLs). Recently, we developed an enzyme-linked immunosorbent assay (ELISA) system for detecting serum granulysin, and reported that serum granulysin is a useful marker to evaluate the cell-mediated immunity. In this study, we show that the serum levels of granulysin were significantly elevated in pre-eclamptic patients compared with those in normal pregnancy subjects. In addition, the serum granulysin levels in pre-eclamptic patients were well associated with mean blood pressure, percentage of peripheral blood Th1 cells and Th1/Th2 ratios. The present results suggest that the serum granulysin levels would be a useful and novel serum marker to evaluate the Th1/Th2 balance, especially Th1 type immunity in pre-eclampsia.