The polyamines spermidine (SPD) and spermine (SPM) are implicated in nerve cell degeneration and regeneration. Over 70% of circulating polyamines are associated with red blood cells (RBC). Against this background we have analysed RBC polyamines in two neurodegenerative disorders, amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). Twenty patients with the sporadic form of ALS, 20 patients with PD, and 20 healthy controls were studied. The highest levels of SPD and SPM were found in the PD group where the mean values were 134 and 115%, respectively, above those of the controls. The patients with PD also presented the lowest levels of the SPD precursor, putrescine (PUTR). In the patients suffering from ALS the SPD and SPM mean levels were increased by 46 and 112%, respectively. The RBC SPD/SPM ratio in the patients suffering from PD was significantly elevated in comparison with that of ALS patient group, suggesting a different involvement of the polyamine system in these disorders. It is at present unknown if raised polyamine levels may contribute to induce the degeneration of susceptible neurons or if the increase represents a compensatory protective reaction, or simply an unspecific epiphenomenon.