Abstract: A portable ladder assembly comprises a base, a supporting bracket, and a single rail ladder. The ladder assembly is particularly well suited for safely allowing human entry into a chamber with a confined area entry, such as a conventional manhole. The base member includes arms positionable on each side of the manhole entry for engaging a support surface, such as the ground, to prevent tipping of the ladder assembly. The bracket includes a rail receiving slot and a plurality of vertically spaced and downwardly directed rung receiving slots on opposing sides of the rail receiving slot. The ladder may be safely supported at various selected depths within the manhole by fitting the rail in selected rungs within their corresponding slots. The ladder assembly of the present invention does not significantly reduce the entry opening into the chamber, and may be safely used without being structurally dependent upon the manhole.