Poly(chloro‐p‐xylylene) was synthesized in a manner similar to poly(p‐xylylene) using Gorham's method at various cryogenic temperatures. The effect of the sublimation rate of dimer on the kinetics of deposition, crystallinity, and crystalline structure was studied. Increasing the sublimation rate of the dimer increases the deposition rate similar to that of poly(p‐xylylene). However, an increase in crystallinity, in contrast to Parylene N, is observed, although, in general, Parylene C has lower crystallinity relative to Parylene N. No polymorphism is observed either by decreasing the deposition temperature or by increasing the sublimation rate of the dimer. Solution annealing and isothermal annealing both bring about crystallization without any structural transformation. Solution annealing removes the oligomers and dimers, but no crystalline oligomers are ever detected under the scanning electron microscope (SEM). The surface topology of films synthesized from ambient temperature to −40°C is very similar to Parylene N. At lower temperatures, in the region −50 to −60°C, a rod‐type morphology is observed similar to Parylene N. The surface topology of samples synthesized at −196°C is totally different from that of Parylene N. All low temperature synthesized samples are amorphous. Copyright © 1987 John Wiley & Sons, Inc.