False twisted synthetic yarn is produced by supplying a continuous multifilament yarn 10 from a supply package 12 through a heater 30 to a false twisting device 14. The supply of yarn to the false twist device is intermittently and randomly varied, for example by electromagnetically controlled tension disc apparatus 26, and the false twist device is preferably driven at a speed to produce a twist multiple between 250 and 450 in the multifilament yarn. The yarn is allowed to set after false twisting, for which purpose a secondary heater 37 may be employed, and the textured yarn is finally taken up on the package 42. The yarn produced may have variable molecular orientation, bulk, torque, twist and shrinkage along its length. It is especially useful in the production of velvet-type upholstery fabric and provides unusual visual effects owing to its variable dye affinity.