Abstract: An extendible and retractable mast is shown which features a tubular body having telescopic sections carried therein. A travelling carriage is driven by means of a winch over associated sheaves to sequentially engage the trailing ends of the telescopic sections for moving the sections between a collapsed position and any desired degree of elevation projecting from the upper end of the tubular body. A series of locking cams allow each telescopic section to be locked into position at a desired degree of elevation. A power assist is provided for assisting the retraction of the telescopic sections.