Laser cutting of corners in sheet metal has been investigated and the influence of the laser power on the cut quality at corners examined. The international standard for thermal cutting has been modified to assess the quality of the laser cut section. Artificial neural networks are introduced to classify the striation patterns formed on the kerf surface. Two thicknesses of work piece were chosen. Oxygen was used as assisting gas during cutting. SEM and optical microscopy were carried out on the cut surfaces. It was found that burning sideways occurs at cut edges in the region of the corners. This was more pronounced with high laser powers and thick work pieces.