The importance of molybdenum, in industry, in life processes, etc., necessitates ac­ curate and precise analytical methods to determine its presence and its concentra­ tion in a variety of samples. With different samples molybdenum is present, as a major constituent, as a minor constituent, as one of several alloying components, as a trace element, and possibly in different oxidation states. The analyst is required to develop more selective and sensitive procedures for determining molyb­ denum in any sample type and new and improved methods for molybdenum are appearing in the literature at an ever increasing rate. It is the purpose of this work to summarize presently available methods for determining molybdenum. It proceeds in two parts. The first discusses procedures by technique, precipitation, colorimetry, electrochemistry, etc. The second discusses molyb­ denum in specific materials, alloys, biological, environmental, etc. In this latter por­ tion emphasis is placed upon sample treatment to obtain a working solution which can then be processed by the most expedient of the techniques discussed earlier.