A field trial of norfloxacin on bovine 206, swine 222 and poultry 205 with respiratory diseases and diarrhea was conducted from Sept 1, 1990 to Jan 30, 1991 in Inchon and Kyonggi-do. The results are as follows. 1. Guinea pigs and rabbits were dosages 10 and 20 times normal. Ten days of observation saw no side effect. 2. Oral treatment on bovine, swine and poultry showed a curing rate of 82.00∼89.06%(Mean 86.00%), compared with 87.27∼96.36%(Mean 92.24%) by Injection. 3. The curing rate was 81.92% by the fourth treatment. 4. The curing rate with and without the use of adjuvant was 80.00∼100% and 83.60∼93. 10%, respectively, for swine, and 81.82∼100% and 82.00∼97.14% for bovine. 5. The curing rate was more dependent on seriousness of illness, environment and time than age. 6. The main disease causing bacteria of bovine respiratory diseases： Haemolytic Sta 27.62%, Haemolytic Str 33.33%, sum of this bacteria is 60.95%, diarrhea: Haemolytic coliform 80.20%, swine respiratory diseases； Haemophilus Spp 20.95%, Haemolytic Sta 72%, Haemolytic Str 21.90%, Sum of these bacteria is 68.57％, diarrhea; Haemolytic coliform 57.26%, poultry respiratory diseases； mycoplasma Spp 29.52%, Haemolytic Sta 13.33％, Sum of this bacteria is 42.85%, diarrhea； Haemolytic coliform 53.00%. 7. The curing rate of norfloxacin by species of strain, the unidentified bacteria on bovine respiratory diseases was the lowest with 77.78％, the others ranged from 84.21％ to 100％ with most of them over 90%. 8. The loss of clinical sign on bovine and swine was the highest when after 2∼4 application. 9. In terms of antibiotic sensitivity test, norfloxacin was the highest with 84.62∼100％ (mean 90.09％) among eight bacterias, only 5 of 15 antibiotics had a sensitivity of over 56.25%, showing a high degree of tolerance.