A method and apparatus are disclosed for the fabrication of pultruded articles. The apparatus includes a means for heating the interior of a bundle of resin-wetted reinforcing material prior to the bundle passing into a heating forming die which heats the exterior of the bundle. Insertion of a thermocouple wire into the interior of the bundle prior to the bundle passing into the heated forming die allows the temperature of the bundle interior to be monitored during the curing process that occurs within the heating forming die. Adjustment of the bundle interior temperature relative to the bundle exterior temperature eliminates stresses caused by adverse thermal gradients that normally would exist without the use of such a bundle interior heater. Use of such a bundle interior heater allows the pultrusion of parts having a greater or thicker cross section than those now normally available.