The internal teat sealant OrbeSeal® (Pfizer Animal Health) should prevent new IMI throughout the dry period. The aim of our field studies was to determine the efficacy of infusion with an internal teat seal at dry off in reducing new intramammary infections during the dry period in relation to an untreated control. In experiment 1 128 cows were enrolled from 24 dairy herds in Lower Saxony. Prior to final milking, all quarters were sampled for bacteriological culture and SCC analysis in three weekly intervals. After final milking, all 4 quarters of test group animals were infused with a commercially available internal teat seal. Following calving quarter milk samples were collected between 1 to 3 DIM and again between 8 to 10 and 15 to 17 DIM for culture and SCC analysis. The rate of new IMI during the dry period was 7.4% of quarters in the OrbeSeal®-group and 12.7% in the control group, resp. In experiment 2 the new infection rate of udder quarters treated with OrbeSeal® was evaluated in a split udder design with 93 cows healthy on all four udder quarters from six dairy farms in North Germany. In this study the front right and rear left udder quarters were treated, while both other quarters served as control. Applied methods occurred like in experiment 1. Here a new infection rate of 2.8% (OrbeSeal® group) and in the control group a new infection rate of 11.5% was reached (P < 0.05).