We propose to develop Iron-57 Nuclear Magnetic Resonance (NMR) as an experimental method for use in the Biomedical Sciences. Numerous molecules essential to life are constructed about iron containing central cores. Among these are hemoglobin, ferridoxin and the cytochromes. To date, no physical chemical methods have allowed direct study of the central metal environment of these proteins. Iron-57 nmr, i.e. the direct detection of the iron nmr signal, holds the promise of being that method.