A direct method of simultaneously polymerizing and forming acetylene monomer to produce uniformly thin films of polyacetylene was investigated in terms of catalyst system, catalyst concentration, and polymerization temperature. The best catalyst was a Ti(OC4H9)(4)-Al(C2H5)(3) system (Al/Ti = 3-4) and the critical concentration was 3 mmole/l. of Ti(OC4H9)(4). Below the critical concentration, only a solid or a powder was obtained. The configuration of the polymers obtained depends strongly upon the polymerization temperature. Thus an all-cis polymer was obtained at temperatures lower than -78 degrees C, whereas an all-trans polymer resulted at temperatures higher than 150 degrees C. Observations either in an electron microscope by direct transmission or in a scanning electron microscope showed that the film is composed of an accumulation of fibrils about 200-300 Angstrom in width and of indefinite length.