Two year old Aleppo pine (Pinus halepensis Mill.) seedlings were exposed to ambient air+50 ppb o3 in open top chambers (24 hours/days, 7 days/week) during May October 1997 and to ambient air+70 ppb concentrations of the current year (c) needles, no were there any differences in photosynthesis or stomatal con,ductance. In May 1998, however, a marked carry-over effect was seen in the chlorophyll a and b and total carotenoid concentrations of the O3 fumigated one year old (c+1) needles. The chlorophyll a and b and total carotenoid concentrations of newly flushed needles of the O3 fumigated seedlings also seemed to be slightly decreased, as was their net photosynthesis when compared to teh values of the filtered air control needles. The chlorotic mottle and the changes in chloroplast pigments and photosynthesis of the c and/or c+1 needles of the NFA+3 seedlings in May 1198 indicate that frequent episodes of ozone concentrations of > 100 ppb, especially when they also occur during the evening and night hours, as in some areas in southern Europe, may result in visible needle damage on Aleppo pine.