A number of case studies were examined to discover how introductory college biology instructors and their students use stories to make sense of biology concepts. Methods involved observing and transcribing stories told by four instructors over two semesters. Three instructors and 31 students were interviewed. Four story types were identified from the study: personal experience stories, historical anecdotes, extended examples, and "you" stories. Four story purposes were also identified: relating, engaging, illustrating change, and cautionary tale. Students found stories useful if they related to real life and were engaging or humorous. Applications for teaching teachers how to use stories effectively are discussed. (Contains 2 tables.)