The question of what students gain by engaging in socioscientific inquiry is addressed in two ways. First, relevant literature is surveyed to build the case that socioscientific issues (SSI) can serve as useful contexts for teaching and learning science content. Studies are reviewed which document student gains in discipline specific content knowledge as well as understandings of the nature of science. SSI are also positioned as vehicles for addressing citizenship education within science classrooms. Although the promotion of citizenship goals seems widely advocated, the specifics of how this may be accomplished remain underdeveloped. To address this issue, we introduce "socioscientific reasoning" as a construct which captures a suite of practices fundamental to the negotiation of SSI. In the second phase of the project, interviews with 24 middle school students from classes engaged in socioscientific inquiry serve as the basis for the development of an emergent rubric for socioscientific reasoning. Variation in practices demonstrated by this sample are explored and implications drawn for advancing socioscientific reasoning as an educationally meaningful and assessable construct. (Contains 3 tables and 3 figures.)