We have examined ten human subjects with a previously developed instrument for near-infrared diffuse spectral imaging of the female breast. The instrument is based on a tandem, planar scan of two collinear optical fibers (one for illumination and one for collection) to image a gently compressed breast in a transmission geometry. The optical data collection features a spatial sampling of 25 points/cm² over the whole breast, and a spectral sampling of 2 points/nm in the 650– 900nm wavelength range. Of the ten human subjects examined, eight are healthy subjects and two are cancer patients with unilateral invasive ductal carcinoma and ductal carcinoma in situ, respectively. For each subject, we generate second-derivative images that identify a network of highly absorbing structures in the breast that we assign to blood vessels. A previously developed paired-wavelength spectral method assigns oxygenation values to the absorbing structures displayed in the second-derivative images. The resulting oxygenation images feature average values over the whole breast that are significantly lower in cancerous breasts (69±14%, n = 2) than in healthy breasts (85±7%, n = 18) (p < 0.01). Furthermore, in the two patients with breast cancer, the average oxygenation values in the cancerous regions are also significantly lower than in the remainder of the breast (invasive ductal carcinoma: 49±11% vs 61±16%, p < 0.01; ductal carcinoma in situ: 58±8% vs 77±11%, p < 0.001).