Three newly developed rice cultures for flash flood affected areas of Assam were evaluated for submergence tolerance with respect to the stage of growth and duration of submergence. Experiments were conducted from 2003 to 2006 at Regional Agricultural Research Station, Titabar. The results showed that all the tested lines were at par with FR13A in their tolerance at vegetative stage while two of the lines viz. TTB 202-3 and TTB202-4 could tolerate submergence better than FR13A These cultivars also exhibited slow degradation of chlorophyll, dry matter and carbohydrate contents under submergence. Significant effect of duration of submergence was observed for different yield attributing characters.