Murine Norovirus is a pathogen in mice that has been known since 2003. Its influence in research findings collected with mice is not sufficiently known by date. On that account mouse colonies have been tested for infection with MNV for a couple of years. In this thesis we established a RT-qPCR Assay for detection of MNV from feces and verified it thoroughly. We investigated the biology of two laboratory MNV strains in mice. The period of shedding and ideal sample collection were investigated. To evaluate circumstances in a field trial, virus shedding of sentinels from our mouse husbandry was quantified additional to serologic routine monitoring and field virus was isolated and propagated. Efficiency of virus detection in feces with RT-qPCR was evaluated. Embryo transfer as a secure method for rederivation from MNV was verified experimentally. For our examinations we established a RT-qPCR assay in contrast to formerly assays carried out with a DNA-standard, conducted with a RNA-standard which equates natural circumstances and validated it according to MIQE guidelines. With this detection method shedding of two MNV-strains, namely MNV-S99 and MNV-4, was tested after oral and intrauterine inoculation. We were able to demonstrate a seroconversion in consequence of intrauterine inoculation of MNV caused by transit virus, but not by replication. After oral inoculation of MNV-4 we demonstrated the existence of replication and therefore excretion of the virus. Shedding of the virus continued, depending on inoculation dosage, longer than expected, namely two to four weeks. After examination of long time shedding we discovered mice shedding for a long time period would shed virus intermittently, hence there is a chance for false negative results. If collecting the feces of mice to be tested after two hours of shedding, the chance to find all mice having shed for a long time is almost 98%. We found out, that transmission of MNV on dirty bedding sentinels in IVCs is not reliable; consequently this method is questionable for monitoring of IVCs. In contrast monitoring by dirty bedding sentinels works very well for open cages. Direct detection of virus in feces of sentinels (in one mouse already in the first week) turned out to be faster than detection of seroconversion (at the earliest in week three). For this kind of husbandry direct as well as indirect detection of virus is an adequate method for routine monitoring. If being particularly interested in having MNV-free mice, additional examinations before the end of examination period would be recommended to identify initial shedding already. One method to eliminate pathogens is embryo transfer technique. This technique has not been tested for MNV until now. Therefore, we tested important organs, ovaries and epididymis, for MNV and didn´t find any virus in the organs of infected mice, neither 103 Summary 104 laboratory nor natural virus. We recommend embryo transfer technique without reservations for rederivation from MNV.