(57) There is disclosed a process for manufacturing monofilament yarn of synthetic material, in which spinning material (3b) is hot extruded through a spinneret (2a) and downwardly through a cooling chamber (4) in which cooling air (A) is directed at the material (3b) to form it into filamentary form. Monofilament yarn is taken-up on a take-up device (9a), and a spin-finish oil emulsion is applied to the extruded material via nozzles 6 at a position close to the take-up device (9a). The take-up speed of the monofilament yarn is at least 4000 m/min, and this factor, in combination with the close arrangement of the nozzles 6 to the take-up device, enables monofilament yarn of the pre-oriented type to be obtained using otherwise conventional equipment of the type suitable for producing multifilament yarn, modified to carry out the process of the invention. The position of the nozzles 6 is at a spacing of between 2500 and 6500mm below the spinneret (2a).