Although observational protocols have been developed that assess different aspects of science teaching, none of the protocols existing in the literature address the principles of effective chemistry instruction guided by Johnstone's triangle of macroscopic, symbolic, and particulate representations of matter (Johnstone, 1991). We developed our own protocol, the Representations in Chemistry Instruction (RICI) protocol, to meet this need. RICI's research-based indicators include: (1) who used the representations (teacher or student) during instruction; (2) the role of representations in improving conceptual understanding; (3) the quality of discourse around the representations; and (4) the degree to which different representations (macroscopic, symbolic and particulate) were integrated in the lesson. The protocol was evaluated for face validity by a panel of chemistry education researchers and for reliability with evaluation of paired observations by two researchers, resulting in a Cohen's kappa of 0.71. The RICI protocol, used with an inquiry-based instruction observation protocol, like the similarly formatted EQUIP (Marshall et al., 2009), can evaluate the quality of secondary chemistry instruction for education researchers and professional development leaders, provide feedback to chemistry teachers for professional growth, and serve as a model for effective use of representations in chemistry instruction.