The objective of this study was to analyze the current situation of laboratory accreditation (LA) in Thailand, especially on occupational and environmental health. The study integrated both quantitative and qualitative approaches. The response rate of the quantitative questionnaires was 54.5% (226/415). The majority of the responders was environmental laboratories located outside hospital and did not have proficiency testing. The majority used ISO 9000, ISO/IEC 17025 or ISO/ EEC Guide 25, and hospital accreditation (HA) as their quality system. However, only 30 laboratories were currently accredited by one of these systems. Qualitative research revealed that international standard for laboratory accreditation for both testing laboratory and calibration laboratory was ISO/IEC Guide 25, which has been currently revised to be ISO/IEC 17025. The National Accreditation Council (NAC) has authorized 2 organizations as Accreditation Bodies (ABs) for LA: Thai Industrial Standards Institute, Ministry of Industry, and Bureau of Laboratory Quality Standards, Department of Medical Sciences, Ministry of Public Health. Regarding LA in HA, HA considered clinical laboratory as only 1 of 31 items for accreditation. Obtaining HA might satisfy the hospital director and his management team, and hence might actually be one of the obstacles for the hospital to further improve their laboratory quality system and apply for ISO/IEC 17025 which was more technically oriented. On the other hand, HA may be viewed as a good start or even a pre-requisite for laboratories in the hospitals to further improve their quality towards ISO/IEC 17025. Interviewing the director of NAC and some key men in some large laboratories revealed several major problems of Thailand's LA. Both Thai Industrial Standards Institute and Bureau of Laboratory Quality Standards did not yet obtain Mutual Recognition Agreement (MRA) with other international ABs. Several governmental bodies had their own standards and accreditation systems, and did not accept other bodies' standards and systems. This put a burden to private laboratories because they had to apply and get accredited from several governmental bodies, but still had to apply and get accredited from international ABs especially for those dealing with exports. There were only few calibration laboratories, not enough for supporting the calibration required for the equipment in testing laboratories' LA. Purchasing proficiency testing specimens from abroad was very expensive, and often got into troubles with the customs duty procedures. The authors recommend some strategies and activities to improve laboratory accreditation in Thailand. Improvement in occupational and environmental health laboratories would essentially be beneficial to laboratory accreditation of other areas such as clinical laboratory.