The heterogeneous reactions of NO3 on NaCl and KBr salt were studied at room temp. using a Knudsen reactor equipped with dual detection, namely Laser induced fluorescence and mass spectrometry. The uptake coeffs. of NO3 were g=(4.9+-3).10-2 onto NaCl and g=0.16+-0.08 onto KBr. In the case of NaCl, HCl was the sole product obsd. However, there is indirect evidence that Cl atoms are the primary products. In the case of KBr we obsd. Br2 and Br to be the products of reaction. A first estn. of the atm. relevance of these reactions indicate that under certain conditions the heterogeneous loss of NO3 on sea-salt aerosols may compete with removal by homogeneous gas phase reactions.