Asking questions is an essential component of the practice of science, but question-asking skills are often underemphasized in science education. In this study, we examined questions written by students as they prepared for laboratory exercises in a senior-level cell biology class. Our goals were to discover 1) what types of questions students asked about laboratory activities, 2) whether the types or quality of questions changed over time, and 3) whether the quality of questions or degree of improvement was related to academic performance. We found a majority of questions were about laboratory outcomes or seeking additional descriptive information about organisms or processes to be studied. Few questions earned the highest possible ranking, which required demonstration of extended thought, integration of information, and/or hypotheses and future experiments, although a majority of students asked such a question at least once. We found no correlation between types of student questions or improvement in questions and final grades. Only a small improvement in overall question quality was seen despite considerable practice at writing questions about science. Our results suggest that improving students' ability to generate higher-order questions may require specific pedagogical intervention. (Contains 5 tables and 1 footnote.)