Hollow particle filled composites are termed as syntactic foams. These composites are known for their low density, ability to absorb considerable amount of energy under compressive loading conditions and controlled mechanical and physical properties. The present paper reviews various parameters related to microballoons, porosity issues and select mechanical properties of polymeric and metallic syntactic foams. Compressive behavior of syntactic foams is the main focus of the discussion. The extended stress-plateau region observed in the compressive stress-strain curves leads to high energy absorption in these materials.