Abstract: In this paper we describe a system to create LEGO models using sketches. Although there are a few applications to create LEGO models, they are difficult to use, mainly due to the searching and manipulation mechanisms that they (do not) offer. Here, we propose a sketch based approach, where users can easily insert parts, by specifying their dimensions through sketches and the system suggests a list of possible parts. To help with the modeling and the manipulation we also developed a constraint based mechanism, which keeps parts connected, performs snapto- grid and detects collisions. Experimental tests with users revealed that our approach is easier and faster to use than a conventional application, such as LeoCAD.