A PROCESS FOR CONTINUOUS PRODUCTION OF A SPINNABLE POLYESTER INCLUDING A PLURALITY OF STEPS OF PRECONDENSATION OAND OF PROGRESSIVE CONDENSATION ACCOMPANIED BY REMOVAL OF GASEOUS CO-PRODUCTS. THE INDIVIDUAL STEPS ARE CARRIED ON APPLYING THIN-LAYER TECHNIQUE WITHIN SEPARATE ENVIRONMENTS AT DIFFERING TEMPERATURE AND PRESSURE CONDITIONS AND WHEREIN THE WALLS DEFINING SAID ENVIRONMENTS ARE SO HEATED TO MAINTAIN THE TEMPERATURE GRADIENT AT THE INTERFACE OF WALL AND LIQUID THIN LAYER WITHIN A SMALL VALUE PREFERABLY NOT GREATER THAN 6*C., AND THE SAID LIQUID THINLAYER IN EACH ENVIRONMENT PREVAILINGLY CONSISTS OF PARTIALLY REACTED PRODUCT RECYCLED IN SAME ENVIRONMENT. AN EQUIPMENT COMRPISING A PLURALITY OF REACTION ENVIRONMENTS, RECYCLING MEANS AND SURFACE HEAT-EXCHANGING MEANS FOR CARRYING OUT THE PROCESS.