Twelve healthy volunteers ingested orally 7-10.5 g of NH4NO3 in a single dose and 12 others received 9.5 g of NaNO3 intravenously in about 60 min. Samples of blood, saliva and urine were collected just before administration of nitrate and at various times afterwards during a 24 h period. Saliva and urine were analysed for volatile NA, nitrate and nitrite. Blood was analysed for nitrate. Neither in urine nor in saliva were NA other than NDMA detected. Of the 188 urine samples, only 13% contained more than 0.1 microgram NDMA/kg, the highest level being 0.5 microgram/kg. In 92% of the 179 saliva samples, less than 0.5 microgram NDMA/1 was found. The saliva of 1 person contained 0.7-8.9 microgram NDMA/1. Nitrate levels in blood rose sharply during the first hour after intravenous nitrate administration and 2 hours after oral intake, reaching peak values of ca. 6 mmol/1. Peak values for NO-3 + NO-2 in saliva, which were reached 2-6 hours after intake, varied strongly between individuals, ranging from 4 to 43 mmol/1. Nitrite was detected in 26% of the urine samples. There was no correlation between NDMA contents and nitrite in urine. An average of 75% of administered nitrate was excreted in urine in 24 h. However, nitrate contents in blood, urine and saliva after 24 h were still higher than before the nitrate intake.