Procedures are presented for the analysis of profiles of purine and pyridine compounds in human and rabbit red blood cells by reversed-phase high-performance liquid chromatography and in Ehrlich ascites tumour cells of mouse by ion-pair high-performance liquid chromatography. These compounds are present in rabbit erythrocytes in higher concentrations than in human blood cells, and in rabbit reticulocytes the concentration of purine compounds is still higher. During glucose-free incubation, human red cells accumulate adenosine and adenine in the presence of coformycin owing to the inhibition of adenosine and AMP deamination. Ehrlich ascites tumour cells lose major portions of purine mono-, di- and triphosphates between the seventh and eleventh day after inoculation into mouse peritoneal cavities.