A silver nitrate test is described for the quantitative determination of residual hypo in photographic prints. The hypo is converted in situ to silver sulfide, the transmission density of the sulfide determined, and the hypo content obtained by reference to a standard curve. The method used to establish the standard curve is outlined, the data being verified by quantitative analyses. A simplified procedure is suggested involving the application of a drop of silver nitrate to the back of the print and then matching the spot visually with a set of standards.