The study of cattle respiratory diseases during the last decade show that several observations made in the late 1960s are still relevant today. Many of these diseases are shared with other countries in Europe, but the developments discussed will be examined with the respiratory disease problems that occur in Britain in mind. The new information is dealth with as it applies to (i) structure, function and immunology of the lungs (ii) diseases of calves indoors (iii) diseases of young animals grazing, (iv) diseases of adult animals indoors and (v) diseases of adult animals grazing.