The expression of pS2 estrogen-inducible protein was investigated using formalin-fixed, paraffin-embedded sections from 210 primary breast cancers. One hundred and three (49%) out of 210 cases were positive for pS2. A significant correlation existed between pS2 expression and hormone receptor status. Patients with pS2 expression had better overall survival and a longer survival time after the first recurrence than those without pS2 expression. By multivariate analysis, pS2 was not an independent prognostic indicator, but pS2 expression was a possible indicator for responsiveness to treatment in relapsed breast cancer patients.