Kalimantan, which has large areas of forest, encompasses a variety of forest types comprising mangrove forest, coastal forest, swamp forest, evergreen tropical rainforest, forest over limestone and heath forest, and stretching from sea level up to 2556 m altitude. The mixed dipterocarp forests are situated mostly in lowland areas, below 600 m altitude. Very few Dipterocarp species occur at high altitudes, i.e., Hopea mengerawan, Shorea curtisii ssp. curtisii, Shorea sp. and Vatica oblongifolia. The high quality timber species Agathis endertii is found only at an altitude of 1450-1600 m, where it mainly grows together with some species of Lithocarpus, Nageia wallichiana and Podocarpus neriifolius. Eugenia spp., Adinandra and Lithocarpus dominate vegetations on the mountain peaks of Mt. Lunjut and Mt. Mencah (Kayan Mentarang National Park). A typical highland species, Weinmannia borneesis is also found here. Tristaniopsis sp. can be dominant on very steep and rocky slopes. Shorea balangeran and Cratoxylum glaucum usually grow on peat or kerangas forests, whereas Gonystylus bancanus, Alstonia pneumatophora, Alstonia spatulata, Combretocarpus rotundatus, Dactylocladus and Lophopetalum javanicum are adapted to the swampy areas. Detailed information on the vegetation (trees) of Sungai Wain Protected Forest in East Kalimantan is presented. In a plot area of 3.6 ha, divided into 9 subplots, 385 tree species with the dbh of 10 cm or more were recorded. These species belong all to 143 genera and 49 families. The species composition in the different subplots sometimes varies greatly. Ranked by importance of species, Shorea laevis, Madhuca kingiana, Eusideroxylon zwageri, Shorea smithiana, Koompassia malaccensis and Drypetes kikir are the dominant species in the subplots.