10 different species of trees from 42 sampling locations were taken in Oyo town, southwest, Nigeria. The barks of these trees were analysed for trace metals: lead, copper, cadmium, chromium, zinc and iron, employing Flame Atomic Absorption Spectrophotometry. The results of the analysis indicate various anthropogenic sources. Mean values of Pb, 3.64 μgg-1; Cu, 8.54 μgg-1; Zn, 20.84 μgg-1 and Cr, 2.02 μgg-1 correlate with the traffic volume of the study area. However, the statistical comparison of some high and low traffic locations did not show significance difference. This study further demonstrate the suitability of Azardiractha indica (Dongoyaro) as a good bio- indicator as well as projecting Ficus vopelli (Odan-abebe) and Terminalia catapa (Indian almond or fruit tree) as also a good bio - monitor .
