In August 1973 and in August 1974 11 macrophytes of a pond-shore community near Bonn (West Germany) were investigated with regard to caloric values and ash content as well as the variability of these parameters. Due to the high constancy of the most important factor, 'availability of water', caloric values varied over rather narrow ranges or did not change at all. Mean values of the caloric determinations were obtained (4157.7 and 4161.2 cal/g dry weight; 4601.2 and 4606.1 cal/g ash-free dry weight) and compared with the data provided by other authors. In Lysimachia vulgaris L., intraspecific variations of the caloric values were determined according to the combustion of flowers, fruits, leaves, and stems.