An open-top chamber experiment with field grown potato (Solanum tuberosum L. cv. Bintje) was performed in the south-west of Sweden in 1998. The experiment was aimed to investigate individual and interactive impacts of elevated ozone (O(3)) and carbon dioxide (CO(2)) on potato growth and yield. Treatments were ambient and elevated CO(2) with or without the addition of 20 nmol mol(-1) O(3). In addition, plants were grown in ambient air plots. Plants grown in elevated CO(2) and O(3) had a reduced tuber yield, compared to control, by 2% and 8%, respectively. These effects were, however, not statistically significant. Elevated CO(2) caused a significantly larger number of tubers of lower average size, while elevated O(3) induced significantly lower tuber dry matter content. The number of tuber initials (tubers <15 mm) found at harvest was significantly lower in elevated O(3). Visible O(3) leaf injury appeared earlier and the number of yellow leaves 89 days after emergence was significantly larger in elevated O(3). In elevated CO(2), haulm dry weight was significantly (15%) lower at harvest and the haulm/tuber ratio was significantly reduced. There were significant interactive effects of O(3) and CO(2) on the final number of leaves and on stem height. Plants in elevated CO(2) reached final stem height earlier than in the other treatments. In summary, it was concluded: (a) that anticipated future O(3) levels are likely to have a negative impact on potato growth, although tuber yield effects may be hard to demonstrate experimentally in this plant due to large variation; (b) that whether any possible beneficial effect of elevated CO(2) on the magnitude of tuber yield will be expressed, depend on the climatic conditions prevailing; and (c) that potato growth responses to CO(2) and O(3) are not simply additive.