Biomass burning events and their effects are investigated using measurements from the Advanced Very High Resolution Radiometer (AVHRR) over Africa in 1997 and South America in 1995. Fires are detected, and aerosol optical thicknesses of the smoke pixels identified from the AVHRR imagery are retrieved using a table look-up approach. The retrieved mean aerosol optical thickness ((tau) 0.64) ranges from 0.3 to 0.6 over Africa and from 1.2 to 1.5 over South America. The top-of-atmosphere (TOA) and surface shortwave aerosol radiative forcings (SWARF) are estimated. Using two different approaches, the mean TOA SWARFs are about -20 and -40 Wm-2, respectively, over Africa and about -50 and -60 Wm-2, respectively, over South America, indicating an aerosol cooling effect. Over four sites where (tau) 0.64 measurements are available, values of aerosol single scattering albedos ((omega) 0) are retrieved and surface downward shortwave irradiances (DSWI) are estimated using a radiative transfer model. Comparison of calculated DSWIs with observed DSWIs shows that, for 9 out of 12 cases, the root-mean-square (RMS) differences are within 35 Wm-2. The largest error is about 70 Wm-2, which is mainly caused by the uncertainties of the retrieved (omega) 0. This suggests that DSWI can be properly estimated from AVHRR measurements if aerosol optical thickness is available.