The selection of a welding process is frequently based on the requirements of the plastic being welded. The melting temperature of the material and its structure play a decisive role here. This article presents comparative investigations into the heated tool, vibration and radiant heater welding of polyethersulphone with a glass fiber content of 30% by weight. The optimum operating point was established for each of the three pro cesses by means of parameter studies. When the welding results were assessed in the short-time tensile test, radiant heater welding was seen to be the best, with affected joining zones that appear relatively homogeneous (i.e., maintain the original fiber geometry) when observed through the microscope. Shortest cycle times are achieved by vibration welding (< 10 sec.). Heated tool and radiant heater welding give cycle times from 30 sec. up to 60 sec , depending on the process parameters.