Abstract: Changbaishan Mountain is a volcano located in the eastern part of Asia between China and Korea.The lake formed from this volcanic action is called Tianchi Lake which is situated on the summit.Outflow of water from the lake forms the Tongtian River which then enters the ErdobaiRiver a short distance downstream.Collection sites throughout this area included riot only the lake and the rivers, but also a few selected sites in the valley floor on either side of the water course.Such habitats as a waterfall, moist rocks, hot springs and moist forest floor were sampled for diatoms. On September 9th and 10th, 1983, 17 diatom collections were made at nine localities.This is the first investigation of diatoms in this area.Two hundred sixty four taxa are reported representing 34 genera, including 2 new varieties, 1 new form, and one new varietal combination.

Key words: diatom, diatom floristics, volcano, volcanic lake