Potted specimens of 27 Swedish native herbs and grasses were exposed to three different ozone concentrations, CF(charcoal filtered air), NF (non-filtered air) and NF+ (1·5 × non-filtered air) in open-top chambers from 2 Julyto 5 August 1994. The species represented a wide range of different plant strategies according to the C-S-R model.The results show that the stress-tolerators, S, had a smaller mean relative growth rate, R¯, during the exposureperiod and also a smaller accumulation of biomass compared with other strategies. The species with theintermediate strategy, CSR, had a R¯ similar to that of the species with a large component of C, the competitorstrategy, and/or R¯ the ruderal strategy, whereas the net accumulation of biomass was smaller in the CSR group.This difference between R¯ and net growth for the CSR species compared to the species of other strategies, can beexplained by a slower growth for the CSR group during the establishment phase. In the present investigation theresponse to ozone was very small regardless of plant strategy, although there was a weak trend towards slowergrowth with higher ozone concentration, 18 out of 27 species having a greater growth in CF than in NF+. Thegrowth of one typical stress-tolerant species, Festuca ovina L., was stimulated significantly by ozone. Visibleinjury, most likely caused by ozone, was noticed in three species, Dactylis glomerata L., Dactylis aschersonianaGraebn. and Phleum alpinum L. Although there were no major restrictions to plant growth in terms of water,nutrients or space in the present open-top chamber experiment, the variability in all climatic factors was as largeas in the ambient air. This might harden the plants and make them less sensitive to ozone compared to plantsgrown in the laboratory under controlled and optimal conditions with low variability.