Imported species of plants or animals tend either to fail or to flourish in a new environment, and it is nearly inevitable that ranch-fenced exotic ungulates will escape to the wild. Successful introduced species tend to spread into all suitable areas, and the likelihood that exotic species will be damaging is great. Prior study of prospective imported species cannot insure either a successful importation or a beneficial result. Yet a thorough preceding review by qualified ecologists and the effective regulation of ungulate importations by national and international agencies, are the only present safeguards against serious economic and environmental damage. Some general truths are proposed to serve as guiding principles for the future.