Some women suffering from leukemia require bone marrow transplantation to be cured. Bone marrow transplantation is associated with a high risk of sterility and some patients are offered fertility preservation by cryopreservation of ovarian cortex. Transplantation of ovarian cortex to women cured of leukemia, who became menopausal, is currently not performed due to the risk of introducing the disease. In this study, individual pieces of ovarian cortex intended for reimplantation from 25 patients with leukemia were transplanted to each of 25 nude mice for 20 weeks. The ovarian cortex was examined before and after transplantation by histology and immunohistochemistry, and reverse transcription quantitative polymerase chain reaction (RT-qPCR) (in the seven patients with a known marker). Seventeen patients had ovarian cortex retrieved when they were in complete remission. Before transplantation four of seven pieces (two from patients in complete remission) of ovarian cortex had a positive RT-qPCR. After transplantation, none of the mice revealed any sign of disease neither in the pieces of ovarian cortex transplanted nor in any of the murine organs evaluated. Thus, the ovaries from patients in complete remission do not appear to contain viable malignant cells contrasting ovarian tissue retrieved prior to treatment.