S U M M .'\ R '^'In an open-air field exposure system for tbe controlled release of air pollutants, broad bean {Vicia faba L.) crops were exposed to elevated SOj concentrations in tbree growing seasons, in order to analyse tbe etiects on crop growtb under field conditions, Tbe treated plots were exposed to a mean concentration of 165//gm"' in 1985, 62/^g m •' in 1986 and 74/(g m •' in 1988. Tbe background concentration was about 10/(gm"-', A reasonably uniform distribution of SO., concentration was obtained over an area of 8 m x 8 m and concentrations exceeding tbe target concentration were rare. In 1985 and 1988, the growtb rate of tbe crop was depressed at tbe end of tbe pod-filling period, Tbis resulted in a reduction of total dry-matter production of 17",, in 1985 and9",, in 1988, and a seed yield reduction of 23 ",, in 198523 ",, in and 10",, in 198823 ",, in . In 1986, dry matter growtb was not analysed up to tbe end of tbe growing season due to a severe infection of Botrytis fabae (Cboclate spot disease) infection in tbe control plot in tbe middle of tbe pod-filling period. Sligbt B. fabae infections in tbe control plots only were also observed in 1985 and 1988. In all experiments no significant reductions of dry matter growtb were observed in tbe vegetative and early reproductive pbases.