Evidence that adverse rearing environments exert negative effects particularly on children and adults presumed ―vulnerable? for temperamental or genetic reasons may actually reflect something else: heightened susceptibility to the negative effects of risky environments and to the beneficial effects of supportive environments. Building on Belsky’s (1997, 2005; Belsky & Pluess, 2009) evolutionary-inspired differential susceptibility hypothesis stipulating that some individuals, including children, are more affected?both for better and for worse?by their environmental exposures and developmental experiences, recent research consistent with this claim is reviewed. It reveals that in many cases, including both observational field studies and experimental intervention ones, putatively vulnerable children and adults are especially susceptible to both positive and negative environmental effects. In addition to reviewing relevant evidence, unknowns in the differential-susceptibility equation are highlighted.