The release of carbon gases other than carbon dioxide was at no time found to be significant. Patterns of carbon dioxide evolution were highly characteristic of a particular decay process. Two major types of decay were established: that of winter and spring, when decomposition was due entirely to the activity of microorganisms within the carrion system, and that of summer and autumn, when carcases were infested with blowfly larvae. In winter and spring, after an initial period of 18 d, the rate of carbon dioxide production from within the carcase steadied to between 15-20 [L CO2 per g dry wt carcase per hour. Fluctuations about the mean are shown to be closely correlated with changes in temperature. In summer and autumn evolution of carbon dioxide from the carrion rose rapidly with the hataching of the blowfly larvae within the corpse. Within 4-5 d of the hatching of the maggots, rate of carbon dioxide production reached a maximum of 260-270 Il CO2 per g dry wt carcase per hour. This rate of release was maintained but briefly: within a further 3-4 d, production of carbon dioxide fell rapidly to zero. Despite the differences between the patterns of carbon dioxide release characteristic of these two types of decay, the total amounts of carbon dioxide evolved remain very similar. Thus a total of 24-28 il CO2 per g dry wt carcase are released from within the carcase and from leachate under each decay regime.