Efforts to harmonize Good Laboratory Practice (GLP) requirements have been underway through the Organization for Economic Cooperation and Development (OECD) since 1981. In 1985, a GLP panel was established to facilitate the practical implementation of the OECD/GLP program. Through the OECD/GLP program, Memoranda of Understanding (MOU) agreements which foster requirements for reciprocal data and study acceptance and unified GLP standards have been developed among member countries. Three OECD Consensus Workshops and three inspectors training workshops have been held. In concert with these efforts, several OECD countries have developed GLP accreditation programs, managed by local health and environmental ministries. In addition, Canada and the United States are investigating Laboratory Accreditation programs for environmental monitoring assessment and GLP-regulated studies. In the European Community (EC), the need for quality standards specifying requirements for production and international trade has promoted International Standards Organization (ISO) certification for certain products. ISO-9000 standards identify requirements for certification of quality systems. These certification programs may affect the trade and market of laboratories conducting GLP studies. Two goals identified by these efforts are common to both programs: first, harmonization and recognition of requirements, and second, confidence in the rigor of program components used to assess the integrity of data produced and study activities. This confidence can be promoted, in part, through laboratory inspection and screening processes. However, the question remains, will data produced by sanctioned laboratories be mutually accepted on an international basis?(ABSTRACT TRUNCATED AT 250 WORDS)