New or recently introduced weeds are biological pollutants in our natural and agricultural ecosystems. Unlike chemical pollutants, new weeds left unchecked often proliferate and pose problems that may not become apparent until eradication is too expensive or impractical. Management strategies for weeds should include: 1. prevention (from entering foreign commerce); 2. exclusion (detection of weed contaminants in imported products at ports of entry); 3. detection, containment, and eradication of incipient infestations; and 4. perpetual control (of widespread species that cannot otherwise be addressed). Appropriate legislative authority, modern weed technology, funding, and a renewed commitment to the concept of prevention are needed to prevent the introduction of new weeds. A national initiative to prevent the establishment of new weeds would be beneficial by saving on future losses and perpetual control costs. Actions taken now will prevent the continued introduction and spread of new weeds in the United States.