Ultra high molecular weight polyethylene (UHMWPE) monofilaments areconsidered as futurematerial for high performance lightweightcomposites. This prospect is mainly based on their high specific tensile strength, whichis the resultof an optimized gel-spinning process and amaximizeddraw ratio.Key steps in gel extrusion and spinning fibers from UHMWPE arehomogeneousswelling and gelation,which aredetermined by the raw material properties. In this study, three UHMWPE powderswith different average molecular weights and particle morphology were studied regarding their influence on swelling and spinnability of gel-spun UHMWPE monofilaments.The monofilaments were prepared by gel-spinning on a twin screw extruder using paraffin as solvent, followed by solvent extraction in xylene, and ultra-high drawing on heated godets.The testing methods applied were thermal analysis, SEM, XRD analysis, and measurement of bulk density and swelling behavior, The results show that the optimalswellingtemperaturedepends onmelt temperature of the raw material and powder particlesize, the swelling speed on melt temperature and particle porosity, and the swelling ratio on average molecular weight, particle size and distribution, andcrystallinity of the UHMWPE powder. Swelling temperature, speed and ratio on their part influence the shish-kebab formation during spinning,as well as theultra-high draw properties of gel-spun UHMWPE monofilaments.