Golf balls having a foam center with regions of different hardness

A golf ball, comprising:

• i) an inner core comprising a foam composition having a geometric center, an outer region, and outer surface, wherein the foam composition is foamed in the center and at least partially-collapsed in the outer region, the inner core having a diameter in the range of about 0.100 to about 1.100 inches and an outer surface hardness (Hinner core surface) and a center hardness (Hinner core center), the Hinner core surface being greater than the Hinner core center to provide a positive hardness gradient in the inner core;
• ii) an outer core layer comprising a non-foamed thermoset or thermoplastic composition, the outer core layer being disposed about the inner core layer and having a thickness in the range of about 0.100 to about 0.750 inches, and an outer surface hardness (Houter surface of OC) and a midpoint hardness (Hmidpoint of OC), wherein the Houter surface of OC is less than the Hmidpoint of OC to provide a negative hardness gradient in the outer core.