A medical procedure and a system are provided so that two visions are obtainable through natural orifices by means of two observational apparatuses , or one the two visions is selectable. The medical procedure through a natural orifice comprises: forming an orifice in a hollow organ by using a device inserted into the hollow organ from a natural orifice of a patient introducing a first observation device from said orifice formed in said hollow organ into an abdominal cavity introducing a second observation device from said orifice formed in said hollow organ into the abdominal cavity arranging said second observation device in a position different from that of said first observation device simultaneously or selectively displaying an image obtained from said first observation device and an image obtained from said second observation device and performing a desired procedure in the abdominal cavity while confirming the images.
