Abstract: A garment such as a sports shirt has concealed ventilation channels; which provide a continuous air channel between permanent openings. In one embodiment, the channels are flexible and non-intrusive and the openings are maintained by springy eyelets The eyelets and channels are attached to the main fabric of the garment providing a robust and a streamlined construction. Another embodiment incorporates active ventilation structures within the channels the structures having a natural vibration frequency matched to a motion frequency spectrum of the wearer. In a further embodiment, the ventilation channels are made of shape memory polymer and change shape in response to changes in temperature.