In this paper we question whether sketching is essential for conceptual designing. In order to test this hypothesis, we conducted think-aloud experiments with expert architects. They were engaged in two separate design processes: where they were not allowed sketch and where they were allowed to sketch. The comparison of design activities in these two conditions was based on a protocol analysis. The results show that there is no significant difference between sketching and not sketching based on three assessments: design outcome, cognitive activity and idea links. This case study shows that sketching is not an essential activity for expert architects in the early phases of conceptual designing.