The present invention relates to a process for sterilizing implantable biomaterials. In particular the invention relates to a process for sterilizing a cross linked collagen based biomaterial comprising contacting said cross linked collagen based biomaterial with a sterilization solution comprising between 3% and 6% v/v propylene oxide and incubating said biomaterial between 30�C and 55�C for greater than 48 hours with the proviso that the sterilization solution does not include alcohol.