This study was performed to elucidate whether endometriotic lesions can affect peripheral blood lymphocyte-subsets. Changes of lymphocyte-subsets of normal healthy women and patients with uterine myoma or endometriosis before and after operation were also examined by using two-color assay methods. The percentage and absolute number of CD57+CD16+ cells [moderately differentiated natural killer (NK) cells] of NK cell subsets in peripheral blood from patients with endometriosis were significantly lower than values from normal healthy women and patients with uterine myoma, while there was no difference in CD4+ and CD8+ lymphocyte-subsets between normal healthy women and patients with uterine myoma or endometriosis. In patients with endometriosis the percentage and absolute number of CD8+CD11+ cells (suppressor T-cells) was significantly increased after operation, while those in patients with urine myoma did not change. On the other hand, resection of endometriotic lesions resulted in a significant decrease of the percentage of CD57+CD16- cells (immature NK cells) and a significant increase of not only the percentage but also the absolute number of CD57+CD16+ cells (moderately differentiated NK cells), suggesting that existence of endometriotic lesions disturbs differentiation of the NK cells. Furthermore, suppressor inducer T-cells as shown by measuring CD4+2H4+ and CD4+4B4- cells were significantly increased after operation of endometriosis.(ABSTRACT TRUNCATED AT 250 WORDS)