The heat transfer effects during laser cutting of AISI 1018 steel were studied both experimentally and theoretically. The quality of the cut as defined by the kerf width, the oxidation heat affected zone (HAZ), and the heat-treated heat affected zone were measured at all points along the cut, both for the upper and lower surfaces. The oxidation heat affected zone was found to predict the heat-treated region fairly well. The kerf width and the oxidation HAZ variation with the laser beam velocity, power, and oxygen gas pressure were also studied. The results showed that of the above variables, the beam velocity had the most effect on the cut quality;Temperatures were measured adjacent to the cut with thermocouples mounted intrinsically on the sample surface. Temperatures in and around the cutting region were also measured with an infrared sensor. The temperatures were affected by the process variables and the cut quality. Attempts at predicting the cut quality from the recorded temperature data were fairly successful;Two models of the cutting process were also developed. A simple thermodynamic model and a two-dimensional finite element model were quite successful in predicting the cut quality. The models also included the effects of the oxidation reaction and the convective cooling of the oxygen gas jet.