Previous investigations on commercial dairy farms in Brandenburg have shown more than 90% resistance in 60 tested populations of Musca domestica against routinely used pyrethroids. Resistance of M. domestica against pyrethroids was also detected in another study on commercial pig farms in Schleswig-Holstein. Stable flies (Stomoxys calcitrans) are hematophagous insects (both females and males) with a worldwide distribution. Despite their considerable economic importance, their capacity of developing insecticide resistance as well as their negative impact on animal well-being in case of massive occurrence, no recent investigations exist in Germany with regard to the existence of insecticide resistance. However, BVL and FU Berlin jointly initiated an investigation of the occurrence of insecticide resistance in S. calcitrans on commercial dairy farms in Brandenburg during 2015. The results clearly indicated for the first time the presence of insecticide resistance in this species. Questionnaires and farm visits confirmed a frequent and uncontrolled use of pyrethroids for the control of target insects. Based on these findings further investigations are proposed, aiming at a genotypic characterization of resistance in M. domestica and S. calcitrans. The identification of genetic markers should allow a rapid confirmation of resistance and also preventive measures for control and management of the target insects.