The purpose of this study is to investigate and characterize the errors in cognitive processes deployed in the comprehension of procedural texts found on pharmaceutical labels by subjects of different cultural and educational backgrounds. In this study, participants were asked to read and interpret three pharmaceutical labels related to children's medications of varying complexity: oral rehydration therapy (ORT); over-the-counter cough medicine; and over-the-counter fever medicine. Results indicate that: (1) all groups of participants had considerable difficulty in interpreting the instructions; (2), cultural and educational background appeared to be only weakly related to the accuracy of dosage and administration; and (3) errors of comprehension were related to three features of the texts: situation-representational complexity, inherent quantification complexity, and conformity with intuitive models of therapy based on prior knowledge. The results are discussed in terms of the role of multiple representations (boundary objects) and theories of text comprehension to facilitate the reduction of errors.