This study examined the effects of students' characteristics (gender, age, and first-language spoken at home) on their perceptions about problem-based learning (PBL). The study revealed that students from the fifth, sixth and seventh grades perceived PBL in a positive way but there were significant differences between the grades. The resources identified by students as the most useful to their self-directed learning in the PBL unit varied between these grades. However, other parameters such as gender and first-language spoken at home did not have effects on students' perceptions. (Contains 2 figures and 5 tables.)