The extensive karst areas of the Lao PDR are poorly documented but are known to include extensive limestone mountain plateaus; isolated ridges including towerkarst; hillslopes that are locally underlain by limestone; and alluvium-covered limestone plains. Palaeokarst phenomena attest to a very long history of karstification while sediments in some caves offer insight into environmental change during the Quaternary. Limited financial and technical resources, political factors and the dangers posed by massive volumes of unexploded ordnance that remain after decades of war are major impediments to karst area documentation, analysis, planning and management. Assessment of karst extent based on aerial photographs and other remote sensing techniques is complicated by very extensive pseudokarst formed due to bombardment during past military con*icts, including hundreds of thousands of closed depressions formed in both carbonate and non-carbonate rocks. Notwithstanding such practical di+culties, the extent and importance of the karst is such that improved inventory at the national, provincial and local levels is required if satisfactory environmental management and sustainable social and economic development are to be achieved.