Abstract: A process for producing a transparent and heat-resistant container includes forming a sheet from a melt of a polyester resin having at least 80 mole % ester units derived from 1,3-propanediol and terephthalic acid or an ester-forming derivative thereof. The formed sheet is quenched and solidified so as to have relatively low crystallinity (i.e., less than 50%). The solidified low crystallinity film is then aged and shaped by thermoforming to obtain a container having relatively high crystallinity (i.e., greater than 50%, and preferably greater than 80%). The aging step is most preferably conducted at a temperature which satisfies the relationship represented by the following equation (1):Ta.ltoreq.Tccwherein Ta is the aging temperature (.degree.C.), and Tcc is the cold crystallization temperature (.degree.C.) as determined by differential thermal analysis at a rate of temperature increase of 10.degree. C./min.