Abstract: A polyester container particularly adapted for hot fill applications having an improved base configuration. The container base has an outer circular ring defining a support plane for the container with a central outwardly concave dome portion therein. The dome portion includes a number of reinforcing rings formed along concentric tangent lines. In accordance with several embodiments, the circular rings are uninterrupted, whereas in other embodiments, the rings are interrupted at regular angular intervals with relatively smooth zones or hemispherical pockets therebetween. The containers provide excellent mechanical stability in response to positive and negative pressure within the container, and also in response to unrelaxed retractive stresses within the container material which tend to cause deformation of the container, particularly when exposed to elevated temperatures during demolding of the container and during the hot fill cycle.