A survey of morbidity and mortality was undertaken in a slatted unit containing 6399 beef cattle over a 6 month period. The mortality rate was 0.78% and the morbidity rate was 12.7%. The interval from arrival to morbidity was 25.5 days +/- 0.9. Significantly more sick cattle were identified on either Mondays or Tuesdays than were seen on Saturdays or Sundays (P < 0.005). The mean interval to mortality (all diseases) was 48.5 days +/- 7.4. Respiratory disease was the most frequently recorded disease and was responsible for 62% of morbidity and 58% of mortality. Samples from 133 cattle, taken as they presented with acute onset respiratory disease, contained antibodies to Bovine Herpes Virus -1(BHV-1) (14.3%), Bovine Viral Diarrhoea Virus (BVDV) (78%), Bovine Respiratory Syncytial Virus (BRSV) (94%) and Parainfluenza type 1 Virus (P13V) (99%). When the same cattle were resampled 4 to 6 weeks later antibodies were found for BHV-1 (93.2%), BVDV (99.2%), BRSV (100%) and P13V (100%). Eleven of 27 bronchoalveolar lavage samples taken from the above group of cattle exhibited positive fluorescence for BHV-1 but all 27 samples were negative for BVDV, BRSV and P13V. Pasteurella multocida was isolated from eight of the 27 lavage samples and Pasteurella haemolytica from one sample.