Abstract: A method of producing a casein film, in the form of a planar film or a film tube, by mixing an aqueous solution containing at least one partly volatile carboxylic acid, at least one plasticizer and deionized water, with casein, and causing the mixture to swell, deforming the swollen mixture at temperatures of from 60.degree. C. to 100.degree. C. to obtain a film or a film tube; solidifying the film or film tube by treatment with an aqueous hardening solution and, optionally, by cold-smoking, and drying the film or film tube. The films have excellent packaging characteristics and are biodegradable. They are especially suited for use as edible sausage casings, packaging material for non-hygroscopic, powdery or fat-containing products, for packaging tablets and aromatic dry products, in the production of seed strips and adhesive tapes, and for lining paper.