Glatiramer acetate, formerly known as copolymer 1, is a mixture of synthetic polypeptides composed of four amino acids. Glatiramer acetate has been shown to be effective in preventing and suppressing experimental autoimmune encephalitis (EAE), the animal model of multiple sclerosis (MS). Therefore it was tested in several clinical studies, where it was found to slow the progression of disability and to reduce the relapse rate and the magnetic resonance imaging (MRI)-defined disease activity and burden in relapsing-remitting MS. As a daily standard dose, 20mg of glatiramer acetate is injected subcutaneously. After injection, glatiramer acetate undergoes rapid degradation to amino acids and shorter peptides; so it is not possible to measure any systemic plasma concentrations or excretion rates. Two major mechanisms have been proposed to explain the effects of glatiramer acetate in EAE and MS: the induction of glatiramer acetate-reactive T helper 2 (Th2)-like regulatory suppressive cells and the interference with T cell activation as an altered peptide ligand. The most common adverse effects were mild injection site reactions (erythema, inflammation and induration). The most remarkable adverse event is the acute and transient immediate postinjection reaction manifested by flushing, chest tightness, palpitations and dyspnoea. Other reported adverse effects are transient chest pain and lymphadenopathy. Antibodies to glatiramer acetate induced during treatment do not interfere with its clinical effects. In several controlled clinical studies, glatiramer acetate has been shown to provide consistent, reproducible clinical benefits in the target population of patients with relapsing-remitting MS. The safety profile and risk-benefit ratio are excellent. Overall, glatiramer acetate is very well tolerated and has an excellent risk-benefit profile in patients with relapsing-remitting MS.