A water-in-oil emulsion explosive composition having a remarkably improved storage stability in its initiation sensitivity in small diameter cartridges and at low temperatures is disclosed. The explosive composition comprises a disperse phase formed of an aqueous oxidizer solution consisting of (a) ammonium nitrate or a mixture of ammonium nitrate and another oxidizer salt, (b) water and (c) a specifically limited weak acid salt or condensed phosphate; a continuous phase consisting of (d) fuel oil and/or wax; (e) an emulsifier; and (f) hollow microspheres or microbubbles.