The heterogeneous chemistry of glyoxal on sulfuric acid surfaces has been investigated at various acid concentrations and temperatures, utilizing a low-pressure fast flow laminar reactor coupled to an ion drift-chemical ionization mass spectrometer (ID-CIMS). The uptake coefficient (gamma) of glyoxal ranges from (1.2 +/- 0.06) x 10(-2) to 2.5 +/- 0.01) x 10(-3) for 60-93 wt % H2SO4, at 253-273 K. The effective Henry's Law constant (H*) ranges from (98.9 +/- 4.9) x 10(5) to (1.6 +/- 0.1) x 10(5) M atm(-1) for 60-93 wt % at 263-273 K. Both the uptake coefficient and Henry's Law constant increase with decreasing acid coneenttation and temperature. Our results reveal a reaction Mechanism of hydration followed by oligomerization for glyoxal on acidic media, indicating an efficient aqueous reaction of glyoxal on hygroscopic particles leading to secondary organic aerosol formation.