Previous studies have shown an abnormality of the spermidine-to- spermine (Spd/Spm) ratio in whole blood of cystic fibrosis homo-and heterozygotes. To investigate Spd and Spm distribution amoung blood components as a possible cause of the abnormality, blood was fractionated using Rabinowitz's glass bead technique and Boyum's Ficoll- Hypaque method. Free (unconjugated) polyamines were extracted with perchloric acid and quantitated on an amino acid analyzer. In controls, mean +/- SEM concentrations in nmoles/10(9) cells of Spd and Spm, respectively, were 1.02 +/- 0.08 and 0.894 +/- 0.28 for erythrocytes; 126 +/- 31 and 357 +/- 105 for lymphocytes; 36 +/- 16 and 240 +/- 33 for granulocytes; and less than 0.5 and less than 0.5 nmoles/ml for plasma. When converted to the concentration in whole blood, it was found that greater than 90% of Spd and over 70% of Spm was associated with erythrocytes. While the higher cellular concentration in leukocytes was not unexpected, the fact that Spd and Spm in whole blood were primarily associated with erythrocytes was a new finding. Comparison with controls revealed that the Spd/Spm ratio in both whole blood and erythrocytes was significantly higher in the group of cystic fibrosis patients.