Starch, glucose, fructose and sucrose were measured in nodes and internodes of horizontal rhizomes of Phragmites australis in two localities, at 400 and 1350 m above see level respectively, before the spring growth started. In the respective localities five and four age categories of rhizomes were distinguished. Rhizomes of lowland plants, harvested on March 21, contained more starch (17.6%), glucose (2.5%) and total non-structural carbohydrates (35.2%) than rhizomes of plants collected at the tree line on June 3 (11.8, 1.7 and 30.5%, repectively). The proportion of water soluble carbohydrates on total non-structural carbohydrates, indicating acclimatisation to a cold climate, was higher in the mountain locality (60 and 49%, respectively). Glucose and starch concentrations increased with rhizome age in both localities whereas all other carbohydrate fractions were independent of locality. Water soluble carbohydrates were preferably accumulated in internodes whereas starch was accumulated in nodes.