Abstract: A panel door having door frame members extending vertically and horizontally therein defining rectangular spaces in which panels are mounted. A panel is mounted in the door with its edge margins seating within channels extending along door frame members surrounding the panel. Fire endurance in the panel is achieved by the inclusion of fire-resistant strips having one set of margins fitted within grooves indented inwardly from the panel's edge margins. The opposite set of margins of the strips are fitted within grooves provided in the bases of the channels.