An in vivo non-invasive method for detecting and/or diagnosing a pathological condition using hyperpolarized .sup.129Xe spectroscopy is disclosed. Generally stated, the method includes determining the magnitude of spectral peaks which represent particular chemical shifts and comparing the observed magnitudes to those of healthy individuals. Preferably, the method includes subtracting substantial backgrounds and accounting for secondary conditions such as the polarization of hyperpolarized gas administered. Additionally, a quantitative analysis of hyperpolarized .sup.129Xe spectra advantageously allows, a physician to establish the extent of disease progression. Advantageously, this method can be used regardless of the method of hyperpolarized .sup.129Xe administration.