This study aimed to evaluate the effectiveness of natural casing treatment with ethanol and aqueous extract of the blackthorn fruits (Prunus spinosa L.) on the quality of vacuum packed Kranjska sausages. Three experimental groups of sample sausages were produced. First sample was a conventional sausage filled in a natural casing, second sample was sausage filled in a natural casing that was previously submerged in ethanol extract of the blackthorn and third sample was sausage filled in a natural casing that was previously submerged in aqueous extract of the blackthorn. The sausages were produced in a industrial conditions, stuffed into the pretreated natural casings, vacuum packaged and stored at 4°C for 60 days. There were no significant differences (p>0.05) in chemical composition and in sensory quality between the different sample sausages. This study has shown that extract of the blackthorn fruits (Prunus spinosa L.) incorporated into natural casing before the filling operation affects the reduction in the number of lactic acid bacteria on the outside surface of sausage samples, in vacuum packed Kranjska sausages, stored 60 days at low temperatures. The sausages with treated casings did not have much better oxidative stability during storage, because the herbal extracts probably did not diffuse into the filling, its amount was too small to significantly affect the decrease of the acid and peroxide number, and TBARS value.