Ionometric determinations indicate that nitrate accumulation does not reach very high levels in pears, apples, cherries and peaches. The examination of samples taken from various experimental plots has shown some variations in nitrate contents of fruits, in relation with the uptake by trees of nitrogen, magnesium and calcium. Other factors liable to affect the nitrate content of fruits have also been examined: maturation level of fruits, application of a growth retardant, types of cultivars. Because of their low nitrate content, the fruits here studied are representative of a class of products well suited to human food requirements.