The purpose of this study was to understand how an 8th grade science class used a structured problem-based learning (PBL) strategy to study volcanoes and to discuss some of the issues that science teachers might encounter when designing and implementing the PBL strategy. This study took place at Collins Middle School, which is located in a cosmopolitan community in Illinois. The PBL lessons, which a teacher taught cooperatively with his student-teacher, required ten class periods to study two real-life volcanic phenomena. The guiding research questions were: (a) in what ways did the teachers (Mr. Brown and Ms. Jones) facilitate student learning about volcanoes using the PBL strategy?; and (b) what were the students' engagements like during the PBL classes on a volcano unit? This study's findings supported three main assertions: first, the teachers' questions and group dynamics guided and facilitated the students' course of learning; second, with the teachers' specific guidance, the students collaboratively built up their supporting evidence; most of the supporting evidence was much more developed than just listing the terms or simple facts on volcanoes; and, third, there existed a tension between the teachers' ideals and the implementation of the PBL strategy. They tended to slip into the traditional role of focusing on scientific facts about volcanoes.