Laser welding has become a standard manufacturing technique, particularly in industries where weld quality and performance are critical, such as the aerospace, nuclear, medical devices and automotive sectors. In many laser welding applications, flaws are not acceptable in the final product, so every weld must be inspected. Post-process inspection is time-consuming and, if a systematic problem develops, many flawed parts could be produced before the problem is identified and corrected. The preferred approach is therefore to perform in-process inspection as the weld is produced. This paper describes a weld process inspection system based on a compact, computer controlled optical spectrometer, which observes the laser welding plume in real time. From the plume spectrum, one is able to determine the temperature of the weld site and the elements present in the fusion zone. A sudden change in weld temperature may indicate a weld flaw, either from a loss of laser energy coupling and therefore a loss of fusion, or from excess energy input and burn-through. An indication of the elements present in the fusion zone can be used for seam tracking or penetration monitoring when dissimilar materials are being joined in the butt or lap configurations, respectively.