Abstract—: A model developed for the description of experimental data on heterogeneous nucleation in disperse systems with metastable dispersed phases is applied to the case of ice nucleation in a water emulsion in decane under methane pressure. Activity spectra are obtained for ice-forming particles in the water–decane–methane system. The frequency of ice nucleation on these particles is calculated. Activities of ice- and clathrate-forming particles in this system are compared. It is shown that small amounts of active particles incorporated into the system from an environment can have a significant effect on ice nucleation.