The Prm1 mouse line is already used extensively for the generation of sterile males. However, smaller laboratories often cannot justify maintaining a breeding colony when they only need a small number of sterile males/year. Consequently, many researchers continue to vasectomise males in order to produce pseudopregnant females for their embryo transfer programmes. In an attempt to reduce the communities dependence on surgical vasectomy we are now making ‘ready to use’ sterile males available through the INFRAFRONTIER/EMMA node located within the Mary Lyon Centre at MRC-Harwell, UK. Frozen embryos are also available if you wish to establish a breeding colony.