Ex vivo biopsy samples (n = 42) from human brain tumors and normal brain have been examined by high-resolution proton magnetic resonance spectroscopy. Parameters from one-dimensional 1H spectra, two-dimensional COSY spectra, and transverse relaxation time (T2) data were used to classify the tumors according to the histopathological diagnoses. The ratio of the area between 3.4 and 3.1 ppm to that between 1.5 and 1.1 ppm distinguished glioblastomas from astrocytomas and normal brain, and appeared to be indicative of malignant potential. In support of the one-dimensional data, cross-peaks in the COSY spectra of brain specimens classified glioblastomas and metastases into one group and the more benign tumors, meningiomas, astrocytomas, and normal brain into a second group. The transverse relaxation of the resonance at 1.3 ppm was fitted by a model with two T2 values. The longer T2 value could be used to distinguish glioblastomas from normal brain, the latter having a much longer long T2 value. Astrocytomas showed a continuum of T2 values between glioblastomas and normal brain, with the grade of the astrocytoma correlating roughly with the value of the long T2 component.