Using proton magnetic resonance spectroscopy (1H MRS) spectra were obtained in vitro from extracts of four types of lung cancer (squamous cell, adenocarcinoma, large cell, small cell) and normal lung. The hydrophilic phase of the chloroform/methanol-water extracts yielded several distinct peaks. Among them the peak areas for cholines, creatines, glycine, and alanine, and their ratios were calculated and used as parameters to characterize different lung tissues. The ratios, cholines/alanine and glycine/alanine, were significantly (P < 0.001 to P < 0.05) higher for the normal lung than lung cancers. Creatines/glycine and creatines/cholines generally provided good discrimination (P < 0.001 to P < 0.05) between any two types of lung cancer. When data were further analyzed by discriminant factor analysis, there was 81.5 to 90.7% accuracy in predicting between normal lung and each cancer type, or among the four types of lung cancer. These results suggested that 1H MRS might be useful as an adjunct modality in the differential diagnosis of lung cancers.