ABSTRACT: Secondary porosity play an important role in the diagenesis of some santstones. Studies after 1970`s have shown that more than half of the porosity in sandstones is secondary in origin. Chemical. Physicochemical, biochemical, physical, and biophysical presses result in secondary porosity through, leaching and shrinkage of rock constituents or through the opening and shrinkage of rock constituents or through the opening of fractures.. Secondary prosity can originate anywhere in the diagenetic history.. Most of secondary prosity in ancient sandstones formed as a result of mesogenetic leaching of the carbonate minerals such as calcite, dolamite and siderite. Secondary porosity resulting from, the dissolution of unstable framework or cement» such as feldspar, carbonate, sulfate or rock fragment is common in sandstone. Recognition, of secondary porosity should be based on multiple evidence because monfractured secondary porosity often mimics primary porosity.. Pétrographie criteria for recognizing secondary porosity Include partial dissolution, molds, inomogeneus packing, oversized pores, carrodedr grains, intraconstltuent pores and fractured grains.