Availability of accurate prognostic factors is vital in making decisions on cancer therapy. We have measured the cytosolic contents of phosphoethanolamine and ethanolamine in tumor tissues of 53 breast cancer patients in an attempt to explore the possibility that these amines could be used as prognostic indicators. The levels of phosphoethanolamine and ethanolamine were determined by high-performance liquid chromatography. The ratios of the molar quantity of these amines or amino acids to that of alanine plus tyrosine, which eluted as a single peak, were used to analyze and compare the results among different tumor samples. The results indicated that the values for phosphoethanolamine or ethanolamine varied significantly more than the values for amino acids, such as glycine plus threonine or glutamine plus serine (these amino acids were eluted as single peaks, respectively). The values for phosphoethanolamine, ethanolamine, and phosphoethanolamine plus ethanolamine were analyzed in relation to several commonly used prognostic factors of breast disease. The results indicated that groups having higher mitotic indices had significantly higher values for phosphoethanolamine or phosphoethanolamine plus ethanolamine than the group having lower mitotic indices. As the stage of the disease increased, the values for phosphoethanolamine plus ethanolamine also seemed to become higher. No correlation, however, was observed between steroid hormone receptor positive and negative groups or between positive and negative groups with regard to involved axillary lymph nodes. The content of phosphoethanolamine or phosphoethanolamine plus ethanolamine in cytosol therefore seems to be correlated with some prognostic indicators.