The aim of this qualitative research is to identify Mexican high school students' emotional experiences in mathematics classes. In order to obtain the data, focus group interviews were carried out with 22 students. The data analysis is based on the theory of the cognitive structure of emotions (Ortony, Clore & Collins, 1988) that specifies the eliciting conditions for each emotion and the variables that affect the intensity of each emotion. The participant students' emotional experiences are composed of (1) Satisfaction and disappointment while solving a problem, (2) Joy or distress emotions when submitting a test, (3) Fear and relief emotions in mathematics classes, (4) Pride and self-reproach emotions when grading a course and (5) Boredom and interest in mathematics classes. [The research reported in this article was supported by several research grants from Research and Graduate Department of National Polytechnic Institute of Mexico and the National Council of Science and Technology of Mexico (CONACYT, Basic Scientific Research 2012). For the complete proceedings, see ED597799. For a related article, see EJ1091418.]