Experimental air-water flow pressure drop data at microgravity conditions are reported in this paper. It is found that the pressure drop in both slug flow and frothy slug-annular flow can be predicted by setting the liquid flowing alone at the total volumetric flow rate of the liquid-gas mixture. It is also found that the parameter C in the Lockhart-Martinelli correlation at microgravity conditions is lower than that at normal gravity condition. This indicates that the interaction effects between the two phases at microgravity are weaker.