The invention relates to high temperature 
isomerization of (E)-1-chloro-3,3,3-trifluoropropene. Disclosed are processes for a high temperature 
isomerization reaction converting (E)-1-chloro-3,3,3-trifluoropropene to (Z)-1-chloro-3,3,3-trifluoropropene. In certain aspects of the invention, such a process includes bringing a feed 
stream into contact with a heated surface, wherein the feed 
stream includes (E)-1-chloro-3,3,3-trifluoropropene or a mixture of (E)-1-chloro-3,3,3-trifluoropropene with (Z)-1-chloro-3,3,3-trifluoropropene. The resulting product 
stream includes (Z)-1-chloro-3,3,3-trifluoropropene and (E)-1-chloro-3,3,3-trifluoropropene, wherein the ratio of (Z) isomer to (E) isomer in the product stream is higher than the ratio of the feed stream. The (E) and (Z) isomers in the product stream may be separated from one another.