This study aimed to evaluate the eff ectiveness of natural casing treatment with ethanol or aqueous extract of the blackthorn fruits (Prunus spinosa L.) on the quality of vacuum packed Kranjska sausages. Three experimental groups of sausages were produced. Firstly, a conventional sausage was fi lled in a natural casing; secondly, sausage was fi lled in a natural casing that was previously submerged in ethanol extract of blackthorn, and; thirdly, sausage was fi lled in a natural casing that was previously submerged in aqueous extract of blackthorn. The sausages were produced in industrial conditions, stuff ed into the pretreated natural casings, vacuum packaged and stored at 4°C for 60 days. There were no signifi cant diff erences (p>0.05) in chemical composition or in sensory quality between the diff erent sausages. This study showed that extract of blackthorn fruits (Prunus spinosa L.) incorporated into natural casing before the fi lling operation reduced the number of lactic acid bacteria on the outside surface of vacuum packed Kranjska sausages stored 60 days at 4°C. The sausages with treated casings did not have much better oxidative stability during storage, likely because the herbal extracts did not diff use into the fi lling, and were present in amounts too small to signifi cantly aff ect decreases of the acid and peroxide numbers, or increases in thiobarbituric acid reactive substance values.