The neuroprotective effects of dietary creatine or cyclocreatine supplementation were studied in mouse model of familial amyotrophic lateral sclerosis, in rats given malonate or 3-nitropropionate neurotoxins (model of Huntington disease), and in mice given 1,2,3,6-tetrahydro-1-methyl-4-phenylpyridine (MPTP) (model of Parkinson disease).Behavioral and brain histol. and biochem. evaluations were performed.Brain levels of creatine, phosphocreatine, lactate, IMP, AMP, ADP, ATP, salicylate, 2,3-DHBA, 2,5-DHBA, tyrosine, and 3-nitrotyrosine were measured in the 3-nitropropionate study.Brain levels of dopamine, 3,4-dihydroxyphenylacetic acid, and homovanillic acid were determined in the MPTP study.The creatine supplementation had neuroprotective effects in all 3 models of neurodegenerative diseases.