Cuttings of Betula pendula were exposed to O₃-free air (control) or 90/40 nl O₃ 1^-1 (day/night) and to high and low supply of macro/micro-nutrients throughout the growing season. O₃ uptake was similar in both nutrient regimes, but in the high-fertilized (HF) plants both formation rate and O₃-induced shedding of leaves was increased relative to the low fertilized (LF) plants under O₃ exposure. O₃-exposed leaves in LF plants approached life spans similar to the LF control. Only leaves of O₃-exposed LF plants displayed distinct increases in the concentrations of sugars and reduced ascorbate, in PEP carboxylase activity and delta(13)C, but the water-use efficiency (WUE) declined and was accompanied by elevated dark respiration, similar to HF plants under O₃ stress. O₃-exposed HF plants based their carbon gain on the new intact leaves, while the foliage area stayed reduced (loss of ageing O-3-injured leaves, suppressed branch formation) as compared with the HF control. In contrast, the O-3-exposed LF plants maintained their foliage area similar to the LF control, although the carbon gain was governed by the O₃-injured leaves. Whole-plant production was overall determined by nutrition, however, both 'strategies' in leaf turn-over were similarly efficient in limiting the proportional O₃-caused reduction in biomass production relative to the corresponding LF and HF controls. However, the O₃-exposed LF plants distinctly altered carbon allocation towards a low root/shoot biomass ratio (RIS), whereas the LF control displayed rather high RIS. The carbon balance of O₃-exposed plants displayed high respiratory costs at low nutrient supply and low WUE (biomass increment/whole-plant transpiration) regardless of nutrition.