Iron availability in potatoes and ferrous sulphate was measured in rats in a 10 d balance study and from a single meal using 59Fe and 55Fe as extrinsic labels. Dried potato samples were incubated in gastric juice in vitro and the amount solubilized was compared with other foods. The relationship between ascorbic acid content of dried potato and Fe solubilization was examined in vitro. In the balance study, the rats absorbed (mean with SE) 15.2 (2.7)% Fe from the diet containing 660 g dried potato/kg and 32.1 (2.8)% Fe from the semi-synthetic diet containing FeSO4. Absorption was higher from the extrinsically-labelled single meal: 49.6 (1.1)% Fe from 59Fe-labelled potato and 62.4 (1.2)% Fe from 59FeSO4. The in vitro experiments showed a much greater solubilization of Fe from potato than from the other foods examined. There was a correlation between Fe solubilization and ascorbic acid content of potatoes (rS 0.76, P less than 0.01). It appears that potatoes contain Fe of moderate availability, possibly higher than most vegetables. They also provide ascorbic acid which may enhance Fe absorption from a meal if present in sufficient quantities. Thus potatoes may make a useful contribution towards the Fe nutriture of the UK population.