The present invention is directed to a high expansion two-component structural foam that expands to about twice its original volume while maintaining good cell structure. The foam of the present invention is based on epoxy resins. Each component of the foam system exhibits storage stability, e.g., no phase separation, yet reacts when combined to provide a cured material having exceptionally good compression strength and modulus. The blowing system used to prepare the foam produces a foam which is uniform in appearance and is essentially free of the large voids often found in conventional two-part thermosettable compositions, even when a relatively large mass is utilized.