We investigated the impact of inquiry-based learning on the situational interest (SI) of senior high school students in a molecular biology class. In part I of our study we designed an inquiry-based learning class as an experimental workshop in an out-of-school student lab and compared it with the participants' regular biology class. The workshop consisted of introducing the students to the context, to the theoretical backgrounds of the applied methods, to lab safety and to the technical handling of lab equipment (theoretical part) and of hands-on activities (practical part). Students reported higher values of triggered SI and the feeling component of maintained SI in the workshop than in the regular class. In the value component of maintained SI, there were no differences. In part II of our study we transferred the contents of the workshops to a teaching unit for school (still consisting of practical parts and theoretical parts) and compared it with the experimental workshops. In the practical part, the students reported higher mean values in triggered SI and in the feeling component of maintained SI in the experimental workshops. There were no differences in the value component between the treatments and between the theoretical and practical parts.