Pridopidine belongs to a new class of compounds known as dopaminergic stabilisers, and results from a small phase 2 study in patients with Huntington's disease suggested that this drug might improve voluntary motor function. We aimed to assess further the effects of pridopidine in patients with Huntington's disease. METHODS: We undertook a 6 month, randomised, double-blind, placebo-controlled trial to assess the efficacy of pridopidine in the treatment of motor deficits in patients with Huntington's disease.