The occurrence of both non-Hodgkin's lymphoma and carcinoma involving the female genital tract of the same patient is rare; we describe three such cases. In case 1, a 56-year-old woman with endometrioid endometrial carcinoma had synchronous follicular lymphoma of the uterus and ovary. In case 2, a 57-year-old woman with diffuse large B-cell lymphoma of the uterine cervix presented 5 years later with an endometrioid endometrial carcinoma. In case 3, a 69-year-old woman with an endometrioid endometrial carcinoma presented with a diffuse large B-cell lymphoma of the vagina 3 years later. In two patients, the non-Hodgkin's lymphoma was unsuspected clinically and would have been missed without biopsy and tissue diagnosis.