Over 100 different organonitrogen compounds have been examined for their ability to extract uranium from aqueous solutions, particularly sulfate solutions, of the types usually encountered in uranium ore processing. The more promising of these have been examined further with respect to other characteristics essential to practical application, especially selectivity for uranium, reagent loss to the aqueous phase, compatibility with practicable diluents, maintenance of adequate extraction power over a range of liquor compositions, and compatibility with practicable stripping methods. Most of the compounds originally considered have been found worthy of only cursory examination. The important outcome on the other hand is that several compounds, specifically several long chain secondary and tertiary amines have been identified as having considerable promise for practicable solvent extraction application.