We found that bright green spots could be observed with eye when the cleaved surface of a p-NA single crystal, which had been stored for a few weeks after cleavage, was irradiated with a 1.06 mu m pulse, an observation which indicates that strong SHG occurred on the crystal surface. The bright spots corresponded to etch pits developed as a result of slow evaporation. Growth of a new phase having an acentrosymmetric structure is probable.