Work place engineering problems are recognized as being complex and ambiguous. However, most of the problems students are asked to solve during their degree programs are classroom problems. Most studies of ambiguity in problem solving have defined ambiguity as a characteristic of the problems. We are interested in understanding how students interpret engineering problems, either creating or resolving ambiguity during their problem solving process. The research question that guides this study is: How is ambiguity manifested by engineering students as they solve problems? This study is part of a larger project examining engineering students' engineering problem solving across different types of engineering problems. Twenty materials engineering students were asked to solve four materials engineering problems during a think-aloud session. For the analysis, points of ambiguity during the problem-solving process were identified as periods in which the students specifically verbalized uncertainty. The points of ambiguity in the transcript were then analyzed through script analysis. More specifically textual instances of ambiguity were linked with three main periods and situational categories: a) the situation that caused the ambiguity, 2) what happened during the point of ambiguity, and 3) the reaction of the student after reaching the point of ambiguity. Results indicated that students experienced points of ambiguity in both closed- and open-ended problems. Several motifs were common to both types of problems, including confusion over how to use given values, not having necessary content knowledge, lack of self-confidence, and difficulty conceptualizing the problem. The lack of constraints inherent in the open-ended problems also caused additional ambiguity among some students. Our findings show that ambiguity can take many forms and is not just a function of the problem structure. Students reach points of ambiguity (e.g., points where they do not know what to do next), due to many factors. Some of these factors represent aspects of their academic and epistemological development. Our analysis to date suggests that students need more comprehensive training and practice to be prepared in facing problems that reflect the work in engineering practice. We are currently examining the data further to identify patterns in their response to ambiguity, which may help in developing pedagogical strategies and tools to support students' ability to successfully solve engineering problems.