Kieburtz et al (see: http://www.huntington-study-group.org/Creatine%20abstract.htm) are conducting a double blind clinical trial of creatine in 50 ambulatory Huntington disease subjects randomized to creatine or placebo. Those randomized to creatine receive 3g for 2 months and then 5g for an additional 2 months. There have been no significant adverse events associated with creatine or significant changes in laboratory tests or vital signs. In the creatine treated group creatine plasma levels approximately doubled (210 ± 335 µM vs. 500 ± 125 µM). Kieburtz et al are currently also conducting a multi-center, double-blind study of creatine in patients with Parkinson's disease, funded by the National Institute of Neurological Disorders and Stroke (NINDS). Recently, Rae et al (2003) reported that creatine supplementation (5 grams per day for 6 weeks) had a significant positive effect (p < 0.0001) on both working memory (backward digit span) and Raven's Advanced Progressive Matrices. These findings suggest a role of brain energy capacity in influencing brain cognitive performance and that creatine via its effects on brain energy metabolism may exert beneficial effects on cognition.