From a Danish dairy herd comprising 350 milking cows data were obtained on all (1010) single, liveborn calves dropped over a three year period. Deaths incurred before, during, and immediately after delivery were not included in the study. The mortality rate up to the first few hours after birth was 10% leaving 910 calves to be included in the present study. The overall respiratory disease (r.d.) attack rate among calves from birth up to the end of the sixth month was 23%; the r.d. case fatality rate was 40%; the r.d. mortality rate was 9%. The mortality rate due to ailments other than r.d. was 11%, and the overall mortality rate during the first six months of life was 20%. The economic impact of r.d. in the herd was evaluated using a disease model which, in mathemathical terms, conceptualizes the basic patterns of the disorders within the calf population. The economic implications of various changes in the prevailing herd health status with respect to r.d. are outlined and discussed (Table VII, IX, XI). Also the economic expectations under different sales policies were studied (Table VIII and X). The study clearly demonstrates the versality of health models and how these may be applied to prepare economic forecasts during periods with rapidly changing market and production conditions.