Studies were conducted during the period 1993–1996 to determine the extent of foliar injury on native plant species and black cherry as may be induced by ambient ozone exposures throughout Switzerland. Particular emphasis was placed on determining foliar injury in Canton Ticino (Ti.) situated in the sub-Alpine region of southern Switzerland. Surveys revealed black cherry to be very sensitive exhibiting an adaxial foliar stipple and leaf reddening at higher elevation plots in the southern-most parts of Ti. Open-top chamber investigations confirmed the foliar response as being due to ambient ozone. Surveys of natural vegetation in proximity to air quality monitoring stations throughout the whole of Switzerland revealed many native plants symptomatic with ozone-like foliar injury. Fumigation studies within CSTR chambers are being used to determine ozone-induced exposure/response relationships. Of the species thus far tested, Viburnum lantana, Morus nigra, Betula pendula, Rumex acetosa and Prunus serotina appear most sensitive.