Methane quantities in excess of pore water saturation will form a free gas phase or a solid gas hydrate, depending on the pressure and temperature of the sediments. In dealing with cores that have high gas concentrations, it is important to estimate the phase properties of the subsurface methane-water system or the depth to the base of the methane hydrate stability zone. These estimates can be based on calculation methods such as those outlined in the JOIDES Safety Manual (Ocean Drilling Program, 1992) or using software packages available in the ship's library (Sloan, 1998). The organic geochemist and chemistry technicians should be prepared to implement appropriate sample procedures if gas hydrates are encountered in cores.