Delonix regia leaves and bark samples were collected from ten sites along the main motorways from urban and industrial areas of the Greater Cairo (Egypt). Samples were analyzed for the following trace metals by using Inductively Coupled Plasma Mass Spectrometer: Pb, Co, Zn, Fe, Ni, Mn, Cu and
Al. Concentrations of the trace metals in leaves were significantly higher (at p <0.05) than in bark and were either within or below the normal ranges. In all the polluted sites, Zn, Co and Ni were the most prevalent and enriched trace metals in the leaves. The Fe concentrations were the highest detected element in the bark in all sites. The ratios of Co, Zn, Ni and Pb concentrations in leaf to bark were high in comparison to the ratios of other metals. The spatial variability of trace metals was only significant (at p <0.05) for Co, Zn and Ni at high probability levels and hangs on the traffic and industrial burden in each site. Our results indicated that Delonix regia is an adequate biomonitor of heavy metals pollution in the Greater Cairo, Egypt.