We report on the room temperature strong (similar to 80%) electroresistance (ER) in the double perovskite with mixed Mn valence: Sr2-xGdxMnTiO6, 0 <= x <= 1. Both, continuous and pulsed current-voltage curves are almost identical which indicates that the observed electroresistance is not associated with heating. This is also supported by simultaneous temperature measurements. ER is negligible (absent) in the x = 0 compound and increases with the increase of Gd content 'x'. The amplitude of ER has a maximum for x = 0.75, suggesting that ER is determined by both the double exchange and the Mn3+ concentration. At the same time, magnetic interactions change from the antiferromagnetic (x = 0) to ferromagnetic ones as x -> 1, thus linking the ER with ferromagnetism. (C) 2011 Elsevier B. V. All rights reserved.