To assess the proliferative activity of glands and stroma in nonspecific chronic endometritis (NCE), we evaluated the plasma and morphologic features. We examined 25 endometrial sections that were coded as inactive for the morphologic features of NCE other than plasma cells and 25 proliferative endometria (PE) as controls. Furthermore, the sections were stained with methyl green pyronin (MGP) to demonstrate plasma cells and proliferative cell nuclear antigen (PCNA) for proliferative activity. The number of plasma cells and the grade of proliferative activity were determined by a semiquantitative scale. The results were compared by using the Mann-Whitney-U-test. Of the 25 inactive endometria cases, 11 were NCE and 14 were either early proliferative endometria (seven cases), lower uterine segments (five cases), or under hormone effect (two cases). The number of plasma cells in NCE was significantly higher than in PE. However, there were cases of NCE without plasma cells and cases of PE containing plasma cells. Proliferative activity was significantly lower in NCE cases than in the PE group (p < 0.05). The diagnosis of NCE should rely more on morphologic abnormalities than on plasma cell criteria. Identification of plasma cells may be useful for diagnosis.