These studies were undertaken to determine the influence of age, sex and the season of slaughter on the quality of bovine lungs utilized as a raw material for the pharmaceutical industry. Investigations were done on 123 animals, divided into four age groups. The groups were: calves, bulls and heifers up to two-years of age, young and old cows. The examined lungs came from cattle slaughtered in winter (January), in spring (April), in summer (July) and autumn (October). The following analyses were carried out: the activity of aprotinin, the content of soluble and crude protein and pH. The obtained results have been statistically evaluated. It has been found out that all factors: age, sex, and the season of slaughter had an effect on the above parameters. The lungs of older animals contained a higher number of crude protein, higher aprotinin activity and pH. Moreover, the highest aprotinin activity as well as the highest crude and soluble protein content have been observed in January. The lungs of bulls contained more crude protein and showed higher aprotinin activity in comparison with heifers, whereas a higher amount of soluble protein was found in heifers’ lungs. No influence of sex and slaughter season on pH value has been confirmed.