Factors affecting seismic amplitudes during their travel in the earth are briefly discussed in this chapter. The data processing issues for restoring the amplitude losses taken place during wave propagation, i.e., travelling of seismic waves from source to reflector and back to the receiver, are attended in Chap.  7 on AVO analysis. The amplitude issues discussed here and in Chap.  7 are also relevant to the seismic inversion applications discussed in Chap.  1 in Volume 2 onwards, especially for the prestack inversion applications. The reliable and successful seismic AVO analysis and inversion applications are only possible after the amplitude losses are restored. Current seismic processing software provides amplitude friendly applications such as successful migration algorithms. The indispensable migration process provides reliable data conditioning and recovery of spherical divergence losses. Further gain recoveries are applied to the seismic gathers after migration as discussed and illustrated in Chap.  7 .