ABSTRACT: Stromal leucocytes in normal premenopausal human endometrium were characterised by an indirect immunperoxidase technique employing a panel of monoclonal antibodies. T cells were scanty in proliferative endometrium but increased in frequency in the secretory phase of the menstrual cycle. An additional population of phenotypically unusual lymphocytes (CD2-positive, CD3-negative) was detected in the stratum functionalis in mid- and late secretory phase endometrium, particularly in areas exhibiting pseudodecidual change. The distribution of these unusual lymphocytes mirrored that of the so-called “endometrial stromal granulocytes,” which have recently been shown to be granulated lymphocytes. Macrophages were common throughout the menstrual cycle. B lymphocytes were detected in lymphoid aggregates in the basalis but rarely in the functionalis.