This work concerns the effect of gas phase properties on incipient flooding in counter-current gas-liquid two-phase flow in small diameter inclined tubes (D <10 mm). The aim is to propose generalized correlations that can be used to predict incipient flooding in small diameter tubes. Experiments were performed in a 7 mm glass tube and at two inclination angles, i.e. 30 and 60 degrees from the horizontal, using water as liquid phase and atmospheric air, He and CO2 as gas phase. Previously proposed correlations for flooding prediction (Pantzali et al., 2008) were suitably adjusted to incorporate the effect of gas phase properties. It has been proved that the flooding curves calculated using the proposed correlations are in good agreement with both the results of the present study and relevant literature data. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.