Salivary flow rate and composition, oral microflora and clinical manifestations of radiation damage were studied in 32 patients treated with external irradiation to head and neck areas. Several parameters were investigated: field arrangement, amount of salivary glands irradiated, clinical manifestations such as dryness of the mouth, taste impairment, dysphagia, salivary secretion and composition, and oral yeast flora. The salivary glands have a greater sensitivity to radiation damage than the gustatory tissues. The decrease in salivary secretion is accompanied by a rise in salivary sodium concentration, and in oral yeast flora. The clinical symptomatology was correlated with the amount of salivary glands irradiated. We found that most of the parotids have to be outside of the treated volume, when the rest of the major salivary glands are irradiated, to prevent severe dryness phenomena.