The content of nucleic acid components in numerous foods, especially carbohydrate-rich ones, has been investigated. The data obtained for bases (purines and pyrimidines) were calculated as nucleic-acid equivalents (RNA or DNA); the IMP content was calculated from the measured content of hypoxanthine. Not only did cultivated plants such as cereals and pulses show a high RNA-equivalent content but also vegetables such as spinach, leek, broccoli, Chinese cabbage and cauliflower. We found the same results in mushrooms including oyster, flat, button (whitecaps) and cep mushrooms. In many vegetarian instant meals, the addition of autolysed or hydrolysed yeast caused a large increase in the purine content. Most natural foods which contain resting cell tissue, such as grains of seed, have only high-molecular-mass nucleic acid components with different concentrations; however, growing cell tissue (e.g. soya-bean sprouts) show, as well as the nucleic acids, some lower-molecular-mass compounds.