Phosphorus-31 magnetic resonance spectroscopy (31P MRS) is currently not accepted as a diagnostic tool in the neuro-oncological practice, although it provides useful non-invasive information about biochemical processes ongoing in the intracranial tumours. This pilot study was aimed to present the diagnostic capability of the 31P MRS in brain tumour examination, even its application on clinical 1.5T MR scanner.Seven patients with brain tumorous lesions (four glioblastomas, one ependymoma, and two lung metastasis) underwent multivoxel in vivo 31P MRS performed on clinical 1.5 T MR scanner within measurement time of 20 minutes. Comparing two selected voxels, one in the tumour and the other one in the normal-appearing brain tissue, enabled to investigate their metabolic differences. Enhanced markers of membrane phospholipids synthesis (significantly increased phosphomonoesters ratios) than markers of their degradation (significantly decreased phosphodiesters ratios) manifested a higher cell proliferation ongoing in tumours. High energetic tumorous tissue demands leading to anaerobic metabolic turnover were present as a significant decline in phosphocreatine ratios and adenosine triphosphates. Intracellular pH evaluation showed a tumorous tendency to alkalize. 31P MRS enables the non-invasive metabolic characterization of intracranial tumours and thus appears to be a clinically useful method for the determination of ongoing tumour pathomechanisms (Fig. 2, Ref. 26). Keywords: brain tumour, 31P MRS, 1.5 Tesla; energetic metabolism.