A review was undertaken to summarise our current understanding of the relationship between nitrate levels in drinking water which have risen significantly over the last thirty years and the incidence of thyroid cancer, which has also risen significantly over this time period. Several meta-analyses have confirmed a relationship between nitrates in drinking water and cancer generally, most notably cancers of the stomach and colon. There is less evidence to support an increased risk of thyroid cancer, mostly through lack of evidence rather than the presence of negative studies. Studies which suggest an increased risk of thyroid cancer with high dietary nitrate intake appear to conflict with evidence that fruit and vegetables have a protective anti-cancer effect. While more research is needed in this area, there is sufficient evidence from the impact of nitrates on the incidence of other cancers to seek to reduce nitrate levels in drinking water.