it has been determined that lichens are excellent indicators of regional air quality, since they are long-lived and totally dependent on atmospheric sources for nutrients. in the summer of 1987, samples of the epiphytic lichen, hypogymnia physodes (l.) nyl. were collected from 46 sites in northwestern ontario, twenty-eight of these sites were sampled around the city of thunder bay, samples were also collected from 6 sites around each of the northwestern ontario communities of kenora, ignace and wawa, morphological observations of the lichens were made before sampling. chemical analyses were carried out and levels of a1, as, cd, cu, fe, hg, mg, pb, sand zn were determined for each sample by atomic emission spectrometry. overall levels of elements were low in relation to levels reported in other literature. the ranges of concentrations (ppm) of elements in h. physodes sampled around thunder bay were as follows: al: 185 - 706; as: 0,9 -7,1; cd: 0,2 - 1,2; cu: 0,8 - 6,9; fe: 114 - 691; hg: 0,6 - 5,8; mg: 69 - 393; pb: 3,9 - 48; s: 42 - 434; zn: 7 - 92, the area to the south and southwest of thunder bay had the highest levels of most elements. the area to the west had the lowest levels. the kenora, ignace and wawa areas had low levels of most elements relative to thunder bay results. levels of contaminants indicated an inverse relationship existed between levels of pollutants and the distance from the pollution source. a number of morphological observations correlated significantly with levels of certain elements, suggesting possible indicator value.