Abstract: Dissolved Organic Carbon (DOC) fluctuations were studied in the surface water of Karnaphuli River near BSCIC industrial estate from May 2001 to October 2001, at monthly intervals. Concentration of DOC varied from 0.120 mg L -1. A minimum was recorded in May 2001, while an increase was observed during October 2001. The DOC concentration seems to be closely related to the growth of phytoplankton and other primary and secondary producers which in turn are affected by water chemistry. So the relationship between temperature and pH with DOC is likely indirect. The fluctuations during the observation period showed a relationship with temperature and pH.