The study for a effect of monitoring on bovine mastitis was conduced for a year from Dec, 1989 to Nov, 1990, Sampling the bulk milk of 350 herds in Inchon city and out of 10 herds among them were carried out herds guidance, CMT, SCC, isolation of pathogens and antibiotic sensitivity tests. The results obtained were summarized as follows 1. Annual mean SCC of 1213 herds was 558, 000 cell /ml 2. The number of SCC below 500, 000 cell /ml to quarters for herds guidance was at 1st 77. 0%, End 84.8% and 3rd 80.4%. The is shown that milk quality was steadly improved. 3. The most number of isolated pathogens of bovine mastitis was Staphylococcus SPP - 402(47.2%) Streptococcus SPP - 80(18.7% ) 4. The highest rate of antibiotic sensitivity test was Stapylococcus SPP - cephalothin(76.7%) Streptococcus SPP - ampicillin(77.5%) Gram negative bacilli - tetracyclin(76.0%) 5. The effect of monitoring on bovine mastitis was improved showing that at 1st 49.0% to 3rd 72.0%