Liquid interferon compositions having a pH between 4.0 and 7.2 are described. The compositions comprise interferon-beta and a stabilizing agent at between about 0.3% and 5% by weight which is an amino acid selected from the group consisting of acidic amino acids, arginine and glycine. If needed, salt is added to provide sufficient ionic strength. The liquid composition has not been previously lyophilized or previously cavitated. The liquid is preferably contained within a vessel having at least one surface in contract with the liquid that is coated with a material inert to adsorption of interferon-beta. A kit for parenteral administration of a liquid interferon formulation and a method for stabilizing liquid interferon compositions are also described.