This paper reports the findings of a study investigating junior secondary school students' perceptions of mathematics classroom learning environments in China. An adapted 'What Is Happening In this Classroom?' questionnaire was administered to a sample of 2324 junior secondary school students from 72 classrooms in six provinces. Data were analyzed using factor analysis, descriptive statistics, two-way ANOVA, and cluster analysis. It was found that Chinese junior secondary students generally did not perceive their mathematics classroom environments very favorably. Grade 9 students were found to perceive their mathematics classroom learning environments less favorably than Grade 7 and Grade 8 students did. Moreover, boys were found to perceive their mathematics classes as more inquiry-oriented and perceive themselves as relatively more mathematically involved, while girls perceived more opportunities for cooperation and knew what was needed to compete in mathematics classes. Three types of mathematics classroom learning environments, namely highly favorable, intermediately favorable, and lowly favorable as perceived by participants were further identified in this study.