Abstract: A ventilating cap essentially consisting of an inner frame and a shell having the shape of an inverted cup and dimensioned to envelop the frame. The frame includes a hat band extending in a closed loop about an axis and ribs attached to the band in circumferentially spaced relationship. The ribs extend from the band in a common axial direction and converge toward the axis. Respective portions of the ribs remote from the band and adjacent to the axis are fastened to each other. The rim portion of the shell is releasably fastened to the outer face of the head band in spaced relationship so as to define an annular ventilating gap, and an opening in the shell aligned with the fastened portions of the ribs may be obstructed at least in part by a larger disc releasably fastened to the ribs.