The present invention relates to a method for preparing an allograft material forming a sterile, lyophilised and virally inactivated membrane obtained from mammalian placenta and consisting of at least one membrane layer, this allograft material being suitable for use as a surgical graft. The at least one membrane layer is defined by an amniotic membrane, a chorionic membrane, a spongy tissue membrane or a chorioamniotic membrane obtained from mammalian placenta. The allograft material obtained according to the method is decellularised, virally inactivated and sterilised, and may be vacuum-stored for a period of up to five years at ambient temperature.
