A survey was conducted of the dietary intake of nitrate and nitrite of 747 people aged 15-74 yr living in four regions in Britain. The mean intakes from food were estimated to be about 95 mg nitrate and 1.4 mg nitrite. Vegetables contributed over 90% of the nitrate intake and cured meats 65% of the nitrite intake. The contribution from drinking-water was estimated to add a further 13.5 mg, about 12% of total intake, but varied greatly depending upon water nitrate concentration. Residents of Oxford and the South-east had a higher intake of dietary nitrate, due to a greater vegetable consumption, whereas those from North Wales and the North-east had a higher nitrite intake due mainly to a greater consumption of bacon. The consumption of relatively low ascorbic acid/high nitrate vegetables was significantly greater in Oxford and the South-east. Smoking appeared to inhibit the uptake of circulating nitrate into the saliva, especially at higher levels of dietary nitrate intake. The efficiency of reduction of nitrate to nitrite in vivo and the effect of differing rates of this conversion on the relative importance of different dietary items as potential sources of nitrite are discussed.