This publication demonstrates how the navigation rules and regulations, in particular, aids to navigation systems on the greater Mekong River could be harmonized. The physical characteristics of the Greater Mekong River is presented with a review of existing aids to navigation systems in Cambodia, China, Lao People's Democratic Republic, Myanmar, Thailand and Viet Nam. The comparative analysis of the commonality and differences in the aids to navigation in different countries in connection with the IALA Maritime Buoyage System and CEVNI/SIGNI is presented. The possible conflict or confusion with other types of aids to navigation in different systems is analysed. The fitness of various marks and buoys to the river conditions and countries' capabilities in production, maintenance and use of them are highlighted.