Many institutions are responding to current research about how students learn science by transforming their general chemistry laboratory curricula to be inquiry-oriented. We present a comparison study of student performance after completing either a traditional or an inquiry stoichiometry experiment. This single laboratory experience was the only difference between two comparison groups enrolled in the same general chemistry course with otherwise traditional labs. Measures used to assess student performance included an open-response question, and ACS multiple-choice test items at various points in the course, as well as observations of students in the laboratory, and interviews. Statistical analysis of data used an ANOVA model, including a covariate to control for students' prior knowledge and skills. Students who completed the inquiry experiment significantly outperformed students who did the traditional experiment on stoichiometry content problems and experimental design tasks. No difference in performance between the groups was found on problems not directly related to the content of the experiment. These results provide evidence that student learning of chemistry content and skills is enhanced by a single inquiry laboratory experience, and suggest that increasing the number and variety of inquiry experiments may lead to greater improvements in performance. This study is part of a larger study examining the impact on student performance of incrementally shifting toward more inquiry experiments in the laboratory portion of general chemistry. (Contains 5 tables, 1 figure, and 3 textboxes.)