Ecological interactions can be positive, negative, or neutral, though to-date negative effects (competition, predation, parasitism, abiotic stress) have received the lion’s share of attention. There has been significant progress in understanding how positive interactions (mutualism, facilitation) influence community structure and ecosystem processes. Despite this newfound attention, less progress has been made in integrating the relative roles of positive and negative interactions into a coherent picture of ecological and evolutionary processes. Interactions commonly classified as mutualism or facilitation are increasingly recognized to be dynamic and context dependent. Mutualism is now sometimes thought of as a reciprocal parasitism that alternates between positive and negative interactions. Consequently, a pairwise interaction that is beneficial to a species in one context can be neutral or negative in other another. While case studies of context-dependent mutualisms have accumulated, there is still little synthesis to predict when and where potential mutualisms or facilitations are likely to emerge. The goal of this symposium will be to form a bridge between the two research areas outlined above. Two principal questions will be addressed. First, can we understand the conditions where mutualism and facilitation develops between pairs of species? Are there attributes of certain communities or environments that foster the development of mutualisms between component species? Second, does an understanding of context-dependency in pairwise interactions allow us to understand how positive interactions work to structure entire communities?