This topic outlines developments in seismic technology as they relate to direct hydrocarbon indicators. It lists the questions an interpreter should address to validate observed hydrocarbon indicators, and explains how to identify the relationship between lithology, a propagating wavelet and the seismic response. How color displays enhance our ability to visually discern data is described. The most important parameters used in employing seismic data as HCIs and why these are important are outlined. The use of frequencies in association with interpretive parameters and HCIs are listed. Major concerns with the use of frequency in subsurface HCI interpretation are identified. It lists the typical considerations that go into seismic velocity analysis. The topic explains the velocity crossover as a function of depth and geologic age for gas- and water-filled sand/shale sequences. Some of the positive and negative outcomes of AVO are outlined. Why a bed that is thinning or pinching will have the clearest seismic expression when tuning thickness is reached is explained. The primary purpose of seismic inverse modeling is described. Four ways that fractured reservoirs can be characterized with data from shear wave investigations are outlined.