Aerosol optical depths were derived from sun photometer measurements in three narrow bands centered at 500, 675, and 875 nm, taken at Ilorin, Nigeria, located in sub-Saharan Africa. Selected results will be presented on the diurnal, seasonal, and interannual variability of spectral aerosol optical depth for two Harmattan seasons, during 1987--1989. At 500 nm values between 0.9--1.6 were quite common while the averages were between 1--1.2.