This contract is to provide for the maintenance and housing of a feral mouse breeding colony. The colony represents a major resource for the Oncogenetics Section, LTIB, NCI and plays an integral part in a study on the role of the mouse mammary tumor virus (MMTV) in the etiology of mammary gland neoplasia: The contractor provides technical help experienced in the handling and husbandry of feral mice, breeding of feral mice and knowledge of requirements for the maintenance of outbred colonies. Tumor tissue, milk and other tissue specimens are provided by the contractor.