The impact of ozone lines on Advanced Microwave Sounding Unit-B (AMSU-B) radiances was investigated using a line-by-line radiative transfer model. The impact is found to be the largest for channel 18 (183.31 ¿ 1.00 GHz), with a maximum up to about 0.5 K. The channels 17 (150 GHz) and 20 (183.31 ¿ 7.00 GHz) are also marginally affected by the ozone lines. The magnitude of the impact shows an interesting dependence on the channel 18 brightness temperature which implies that the effect is not just an offset to the brightness temperature.