Corrosion inhibition of mild steel in 2 M HCl and 1 M H2SO4 by leaf extracts of Occimum viridis (OV) was studied using the gasometric technique at temperatures of 30 and 60 degrees C. The results indicate that the extracts inhibit the corrosion process in both acid media and inhibition efficiency increased with concentration. Synergistic effects increased the inhibition efficiency in the presence of halide additives namely KCl, KBr, KI. Temperature studies revealed a decrease in efficiency with rise in temperature and corrosion activation energies increased in the presence of the extract, probably implying that physical adsorption of cationic species may be responsible for the observed inhibition behaviour. Comparative analysis of the inhibitor adsorption behaviour in 2 M HCl and 1 M H2SO4 as well as the effect halide additives suggest that cationic species may not be the only constituents responsible for the inhibiting action of the extract. (c) 2005 Elsevier B.V. All rights reserved.