AIM OF THE STUDY The aim of the study was to identify the populations of immunosuppressive Treg lymphocytes CD4+CD25+foxp3+and cytotoxic cells CD56+,CD57+, CD3+CD8+CD57+, CD8+ during the development of ectopic pregnancy and to compare their number with that in spontaneous abortion decidua and secretory endometrium. MATERIALS AND METHODS Tissue samples derived from fallopian tube and endometrium were obtained from 44 patients with ectopic pregnancy (20-unrutured, 24-ruptured). The decidual tissue was collected from 18 women with spontaneous abortion-AB and endometrial tissue from 18 women in secretory phase of the cycle. RESULTS The percentage of Treg cells was significantly lower, while the number of CD56+ and CD57+ cytotoxic cells were significantly higher at the implantation site in group Np compared to P. No such differences between these subgroups in the percentages of immune cells were found in the eutopic endometrium The numbers of Treg lymphocytes and CD8+ cells were significantly higher within the fallopian tube compared to the decidua in unruptured ectopic pregnancy. The opposite was observed in ruptured pregnancy group- where the concentration of Treg cells and CD57+ cells was significantly higher in decidua compared to the tubal implantation site. The highest number of CD56+ i CD3+CD8+CD57+ cells was fund In SA decidua compared to group NP, P and E. The implantation site in ruptured pregnancy was typified by the lowest number of Treg cells compared to other groups studied. CONCLUSIONS Perforation of the tubal wall seems to be linked to a concentration of cytotoxic immune cells without an adequate increase of the numbers of suppressive cells compensating for detrimental immune cell response.