This paper describes the results of a comparative study into the approaches used by science undergraduates when solving open-ended problems. This study adopted a pseudo-grounded theory framework to analyse six case studies, one from each of the science disciplines studied. The study involved 70 participants from 5 institutions solving open-ended problems using a think-aloud protocol. Analysis of the data identified a number of different approaches used by each subject group. Participants in psychology, pharmacy and sports rehabilitation used a greater number of novice-like approaches than participants in chemistry, physics and interdisciplinary science. The approaches used by physical science participants were very similar whereas those from pharmacy, sports rehabilitation and psychology were more varied and relied on students' ability to relate to a familiar context. Evaluation of the relative quality of solutions showed variation with discipline.