Presence and frequency of epiphytic macrolichens were measured along an air-quality gradient in Halifax City, NS, Canada. Species frequency plots over distance and multidimensional scaling (MDS) suggested lichen-community changes consistent with expected air-quality changes. A provisional list of air-quality indicators was selected based on: 1) demonstrated variation along the air-quality gradient, 2) frequency across the province, 3) literature values of air-quality sensitivity, and 4) ease of field identification. Indicators were placed in one of three classes: 1) pollution tolerant, 2) intermediate pollution tolerance, and 3) pollution sensitive. MDS analysis suggests an elevation gradient in Nova Scotia and this should be investigated with a further study.