An apparatus for the sterilization/disinfecting of dental and/or surgical instruments, the apparatus comprising: a producing device for producing a disinfecting and/or sterilizing gas composition wherein the gas composition comprises ozone and one or both of hydrogen peroxide and water vapour, the device having a gas outlet for supply of the gas composition; a treating device for receiving and treating, neutralizing or absorbing a residual gas composition, the device having a gas inlet for receipt of the residual gas composition; a sterilization/disinfecting chamber in the form of a flexible or collapsible or deformable container (15, 35), the container having a sealable opening through which a dental/surgical instrument may be placed in the container, and having a container inlet for receiving into the container a disinfecting and/or sterilizing gas composition from the gas outlet of the producing device and a container outlet through which residual gas may be expelled or drawn to the gas inlet of the treating device; a supply conduit for providing fluid communication from the gas outlet to the container inlet; a treating conduit for providing fluid communication from the container outlet to the gas inlet; and an instrument receptacle for receiving holding or retaining the instrument to be sterilized/disinfected, which receptacle comprises materials and/or moving parts configured to cause the entire surface of the instrument to be sterilized/disinfected to be exposed to the disinfecting and/or sterilizing gas composition, wherein the instrument receptacle comprises a tray having a resting surface provided with a plurality of elongate protrusions upon which an elongate instrument may be placed, wherein the elongate protrusions are rollers for manual or automatic rotation, and/or a vibrating surface whereby the instruments are caused to move so as to allow the sterilization/disinfecting gas composition to make contact with the entire surface of the instruments being sterilized. a producing device for producing a disinfecting and/or sterilizing gas composition wherein the gas composition comprises ozone and one or both of hydrogen peroxide and water vapour, the device having a gas outlet for supply of the gas composition; a treating device for receiving and treating, neutralizing or absorbing a residual gas composition, the device having a gas inlet for receipt of the residual gas composition; a sterilization/disinfecting chamber in the form of a flexible or collapsible or deformable container (15, 35), the container having a sealable opening through which a dental/surgical instrument may be placed in the container, and having a container inlet for receiving into the container a disinfecting and/or sterilizing gas composition from the gas outlet of the producing device and a container outlet through which residual gas may be expelled or drawn to the gas inlet of the treating device; a supply conduit for providing fluid communication from the gas outlet to the container inlet; a treating conduit for providing fluid communication from the container outlet to the gas inlet; and an instrument receptacle for receiving holding or retaining the instrument to be sterilized/disinfected, which receptacle comprises materials and/or moving parts configured to cause the entire surface of the instrument to be sterilized/disinfected to be exposed to the disinfecting and/or sterilizing gas composition, wherein the instrument receptacle comprises a tray having a resting surface provided with a plurality of elongate protrusions upon which an elongate instrument may be placed, wherein the elongate protrusions are rollers for manual or automatic rotation, and/or a vibrating surface whereby the instruments are caused to move so as to allow the sterilization/disinfecting gas composition to make contact with the entire surface of the instruments being sterilized. a tray having a resting surface provided with a plurality of elongate protrusions upon which an elongate instrument may be placed, wherein the elongate protrusions are rollers for manual or automatic rotation, and/or a vibrating surface whereby the instruments are caused to move so as to allow the sterilization/disinfecting gas composition to make contact with the entire surface of the instruments being sterilized.