The likely dimensions of an extended earth magnetotail are investigated by considering various published polar cap and magnetotail observations in light of recent knowledge about magnetosphere behavior under different interplanetary magnetic field conditions. It is argued that the magnetotail is highly‐time dependent. During southward field conditions the tail probably attains its maximum radius but is subject to "breaking off" via substorm associated reconnection events which temporarily deplete the flux and reduce the radius. During northward interplanetary conditions more field lines are apt to close near the earth leaving considerably less flux to form any extended tail. Using estimates for both the amount of open polar cap flux and the tail flux at 60 Re, we argue that at 200 Reeither the tail cross section is elongated in the equatorial plane or the average radius is not more than 25 R