The purpose of this study was to use instrumental neutron activation analysis (INAA) to investigate the effectiveness of oak tree leaves as indicators of atmospheric pollution. Leaves were sampled from several different cities in southwestern Ontario, Canada and tested for 16 different trace elements (U, Dy, Ba, Ti, Sr, I, Br, Mg, Cu, Na, V, K, Al, Mn, Cl and Ca). The results show promise for the use of oak leaves as multielemental environmental monitors due to their apparent ability to reflect the overall pollution levels of the vicinity in which they grow. Oak leaves were found to be superior to both birch and maple leaves for monitoring most of the elements studied.