We present an interactive modelling technique, which reconstructs three-dimensional objects from user-drawn twodimensional strokes. We first extract a skeleton from the 2D contour, and the skeleton is used to define an implicit surface that fits the 2D contour. The reconstructed 3D shape has a natural aspect, it is very smooth and can easily be edited and modified using strokes or performing operations on the skeleton. This method is very accessible for non-specialist users and it allows fast and easy shape prototyping. Categories and subject Descriptors: I.3.5 [Computer Graphics] Computational Geometry and Object Modelling. General Terms Algorithms, Design. Keywords Geometric Modelling, Sketches, Implicit surfaces.