Successful colonization of the testicular germinal epithelium by bone marrow stem cells producing spermatozoa of donor genotype is rare.

Background: It is not known whether bone marrow stem cells when injected intravenously for a bone marrow transplant colonize the human testicular epithelium. No previous studies of sperm genotype after bone marrow transplantation are reported.

Objectives: To differentiate host from donor genotype in spermatozoa of men who have undergone successful bone marrow transplants.