A collar rot disease of Hevea brasiliensis had spread in 1987 on seed germination beds for the first time in Sri Lanka, devastating more than 10,000 three months old seedlings. The causal organism was identified as Sclerortium rolfsii Sacc. and its pathogenecity was confirmed. The symptoms were yellowing of leaves and rotting of the stem at the collar region followed by collapse of plants. The presence of white cottony mycelium on the stem and the seed coat was evident. Among seven chemicals evaluated in vitro by poisoned food technique captan (0.02;), thiram (0.02;), formaldehyde (0.05;), benomyl (0.2;) and mancozeb(0.2;) could check the growth of the pathogen successfully. In pot culture trials only formaldehyde (0.12;) and tebuconazole (0.06;) were effective in controlling the pathogen without any phytotoxic effect. The disease was completely checked in traditional burning of soil included as a treatment in pot culture trial and none of the seedlings or hypocotyl region of germinating seeds were found to be affected with S. rolfsii.