Medium and high molecular weight polyester polymers are prepared in syrup form from an ester oligomer. The oligomer is converted to the polymer by polycondensation at elevated pressure and elevated temperature in a nonreactive carrier capable of forming an azeotrope with water. The ester oligomerization or polycondensation reactions desirably are monitored using a non-viscometric technique. The process has a rapid cycle time. The syrup contains the polymer and nonreactive carrier, and may more conveniently be used to make initially non-solid products such as polyester coatings than is the case when employing pelletized solid polyester resins.