The emission cross section for the F-2(5/2)-F-2(7/2) transition of Yb3+ has been determined from absorption and emission measurements of niobosilicate glasses at room temperature. Using systematic variations in the spectroscopic properties, relative to composition, a glass host,vith emission cross sections of >2.00 pm(2) and fluorescence Lifetimes of >0.8 ms is obtained. This glass has advantages over some laser glasses that have been reported in other published papers.