We explored the affective states that students experienced during effortful problem solving activities. We conducted a study where 41 students solved difficult analytical reasoning problems from the Law School Admission Test. Students viewed videos of their faces and screen captures and judged their emotions from a set of 14 states (basic emotions, learning-centered emotions, and neutral) at relevant points in the problem solving process (after new problem is displayed, in the midst of problem solving, after feedback is received). The results indicated that curiosity, frustration, boredom, confusion, happiness, and anxiety were the major emotions that students experienced, while contempt, anger, sadness, fear, disgust, eureka, and surprise were rare. Follow-up analyses on the temporal dynamics of the emotions, their contextual underpinnings, and relationships to problem solving outcomes supported a general characterization of the affective dimension of problem solving. Affective states differ in: (a) their probability of occurrence as regular, routine, or sporadic emotions, (b) their temporal dynamics as persistent or random emotions, (c) their characterizations as product or process related emotions, and (d) whether they were positively or negatively related to problem solving outcomes. A synthesis of our major findings, limitations, resolutions, and implications for affect-sensitive artificial learning environments are discussed. (Contains 2 footnotes, 6 tables, and 4 figures.)