Are there circumstances under which scientists and engineers doing their ordinary jobs can be thought of as participants in a social movement? The technoscientists analyzed in this article are at the forefront of a new way of doing chemistry; they are attempting to redesign chemical products and synthesis pathways to significantly reduce health effects and environmental damage from industrial chemicals. Green chemistry practitioners and entrepreneurs now constitute a small minority of chemists and chemical engineers in the university, government, and corporate (...) sectors, but the innovators gradually are institutionalizing their efforts and winning converts. Drawing on concepts from social movement theory, the authors argue that examining green chemistry as a social movement sheds light on the intentional social organization of emerging scientific and engineering disciplines, advances thinking about the role of expertise in social change, and uncovers a possible pathway toward reconstructing chemical technologies on a more environmentally sustainable basis. The article closes with questions about potential coalitions among green chemists and engineers, regulators, and activist sectors of civil society. (shrink)