This article reports on the experiences and perceptions of K-12 teachers as they engaged in a participatory action research (PAR) project, "Science Across the Curriculum." Although the experiences and professional learning of two of the project participants are highlighted, the challenges that all participants experienced as they conceptualized and implemented action research are also reported. The author concludes that messiness and uncertainty are inherent and necessary elements of action research and that these elements need to be explicit for the benefit of those who engage in and facilitate PAR. (Contains 2 tables and 3 notes.) [Abstract provided in both English and French.]