Safety testing methods are necessary to determine whether new chemicals and products may cause adverse health effects to people, animals, and the environment. While such methods have traditionally involved the use of animals, advances in science and technology and the desire to develop more accurate test methods that reduce, refine, or replace animal use have led to progress in developing alternative methods. However, before such methods can be used for regulatory safety decisions, it is necessary to determine their scientific validity and regulatory acceptability. Scientific validation involves determining the usefulness and limitations of a proposed test method for a specific purpose. Regulatory acceptance involves determining whether the proposed use of the new test method can provide as good or better protection than the current test method or approach. The global use of new alternative test methods requires international agreement on the scientific validity and regulatory acceptability of new test methods. Several countries have developed national validation centers to facilitate and promote the scientific validation and regulatory acceptance of new, revised, and alternative test methods. In the United States, the U.S. National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) and the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) work collaboratively to promote the validation and regulatory acceptance of new, revised, and alternative test methods that are based on sound science and that will provide continued or improved protection of people, animals, and the environment while reducing, refining, and replacing the use of animals where scientifically feasible. ICCVAM was organized in 1997 and U.S. law established it as a permanent interagency committee in 2000. ICCVAM consists of representatives from the 15 Federal regulatory and research agencies that generate, use, require, or provide toxicological testing data to safeguard the health of people, animals, and the environment. NICEATM administers ICCVAM and provides scientific and technical support, including the conduct of high priority validation studies. Many other national validation organizations have been established, including the Japanese Center for the Validation of Alternative Methods (JaCVAM), the European Center for the Validation of Alternative Methods (ECVAM), and of course now the Korean Center for the Validation of Alternative Methods (KoCVAM). Canada, the EU, Japan, and the USA signed a Memorandum of Cooperation on International Cooperation on Alternative Test Methods (ICATM) on April, 2009. The agreement provides for enhanced international cooperation, collaboration, and communication among national validation organizations during the design and conduct of validation studies, independent scientific peer review meetings and reports, and the development of harmonized test method recommendations for regulatory consideration. This cooperation seeks to expedite the international regulatory acceptance of scientifically valid alternative methods. The agreement also allows for new national validation organizations to be included that agree to the provisions of the agreement. Since its establishment, ICCVAM has worked in conjunction with the international community to achieve the regulatory acceptance of 27 alternative test methods that have now been accepted or endorsed by national and international authorities. To ensure continued progress, NICEATM and ICCVAM developed a Five-Year Plan in 2008 in conjunction with member agencies to advance alternative methods. The plan identifies priority areas for research, development, translation, and validation activities necessary to support the regulatory acceptance of alternative methods, and increased national and international collaborations with stakeholders. The plan emphasizes the application of advances in science and technology to the development of new more predictive alternative test methods. Implementation of the NICEATM-ICCVAM five-year plan and expanded international collaborations are expected to result in significant progress on alternative methods that will support improved safety assessments while further reducing, refining, and replacing animal use.