Abstract: An improved process is provided for the formation of a high performance polyester multifilament yarn possessing a high strength and an unusually stable internal structure rendering it particularly suited for use in industrial applications at elevated temperatures. The filaments are melt spun and uniformly quenched under relatively high stress conditions to yield an as-spun filamentary material of relatively high birefringence which is passed in-line from the quench zone to a first draw zone provided at a temperature below the glass transition temperature of the as-spun filamentary material, for example at ambient temperature, where it is drawn. Subsequent drawing follows to achieve at least 85 percent of the maximum draw ratio of the as-spun filamentary material.