Type and shape of crystals and idioblasts in leaf blades of 20 species of Amorphophallus Blume ex Decne. and three species of Pseudodracontium N.E. Br. were studied. The plant specimens were collected from several areas of Thailand between November 2008 and May 2012, and grown in greenhouse condition under 70% of sunlight. The leaflet samples were studied by maceration technique, then observed by light transmission microscope. The type of crystal and idioblasts, number, size, shape of crystals and shape of idioblasts vary from species to species. There were prismaticcrystal cells, druse crystal cells and several shapes of raphides cells. The results shown raphides occurred in all species studied. Four species had three types of crystal. Sixteen species had two types viz. druse and raphide bundle and seven species had only raphide bundle. Prismatic crystals were mostly found in the leaves of Pseudodracontium but it was rarely found in the leaves of Amorphophallus. The types and shapes of crystals and idioblasts could help to identify species.