Of 57 patients with clinically suspected mamma carcinoma 121 samples were analysed by in vitro 1H-NMR spectroscopy at 300 MHz and correlated with histological data. Within the relevant spectral region between 2.7 and 4.1 ppm strong signals were observed from fat, (phosphoryl-) choline, (phospho-) creatine, and carnitine. Furthermore, with high regularity, 8 weak, partly overlapping signals were resolved and attributed to glucose, glycine, threonine, serine, inositol, and sucrose. Their intensities were determined by an iterative fitness program. From the intensity ratios, different kinds of tissue could be distinguished based on spectroscopic criteria. Healthy or mastopathically modified tissue could be discriminated from more than 50% carcinoma affected tissue with a specificity of better than 99.5%. This fact is explained by the lower content of fatty acids in the malignant tissue. Differences between spectra of healthy of mastopathically affected tissue were only small.