Incipient equilibrium hydrate formation conditions for the methane-carbon dioxide-neohexane-water system were obtained by employing the isothermal pressure search method. Two gas mixtures containing 80 and 50% methane respectively on a water-free basis were used. At a given temperature, the incipient hydrate formation pressure from the 80-20 gas mixture with neohexane was found to be lower by about 1 MPa from the hydrate formation pressure for the system without neohexane. This is considered to be an indication that structure H hydrate forms. The results for the 50-50 gas mixture, however, indicate that only below a temperature of approximately 277.5 K it is possible to form structure H hydrate.