Purpose:The importance of glycaemic indices (GI) of starchy foods originates from its linkage with type 2 diabetes mellitus. GI of food items is measured by in vivo method which carries a degree of discomfort. We aim to find the in vitro hydrolysis index (HI) of selected starchy tubers in Sri Lanka. Research Method:The degree of hydrolysis for selected tubers was determined by in vitro starch digestion using the proportion of starch converted into maltose. The HI values of six selected tubers were calculated using the ratio between incremental areas under the hydrolysis curve for the tested tubers and the reference food (white bread).Findings: Among the selected tubers, arrowroot had the highest percentage of hydrolysis within the first 30 minutes. There was a significant difference in the percentage of hydrolysis between 60-90 minutes for the selected tubers and white bread.