The percolation behavior of alumina suspensions is studied by computer simulations. The percolation threshold phi(c), is calculated, determining the key factors that affect its magnitude: the strength of colloid-colloid attraction and the presence of hydrodynamic interactions (Hls). To isolate the effects of His, we compare the results of Brownian Dynamics, which do not include hydrodynamics, with those of Stochastic Rotation Dynamics-Molecular Dynamics, which include hydrodynamics. Our results show that phi(c), decreases with the increase of the attraction between the colloids. The inclusion of His always leads to more elongated structures during the aggregation process, producing a sizable decrease of phi(c) when the colloid-colloid attraction is not too strong. On the other hand, the effects of His on phi(c) tend to become negligible with increasing attraction strength. Our phi(c) values are in good agreement with those estimated by the yield stress model by Flatt and Bowen. (C) 2015 Published by Elsevier inc.