The fourth regional training on monitoring trans-boundary air pollution was held at United Nation Environment Program Regional Resource Centre for Asia and Pacific, Pathumthani, Thailand during 13 to 16 March 2006. The major objectives of the training were to introduce the Quality Control and Quality Assurance (QA/QC) programme; and to discuss the issues encountered in operating the monitoring sites in each country. This regional training program strengthens the monitoring network based on the common methodologies and standards at the national level and to exchange the experience in developing national monitoring stations. The training was organised by UNEP RRC.AP in collaboration with IVL, SEI and AIT. The program was attended by laboratory technicians and in charge of Malé Monitoring Stations in the participating countries as well as the members of Monitoring Committee (MoC), SEI, IVL, UNEP, and AIT.