About 30,000 cows in- California are being screened every month by the California Mastitis Test—CMT—applied to milk samples collected for butterfat determination. Owners of dairy herds which show a high level of CMT-positive cows are receiving advice on management. Where indicated, medical treatment is given during the 2-3 months when the milk producing glands are in the resting or dry state.

The above progress report is based on Research Project No. H 1064.