The invention relates to methods of treating and preventing disorders associated with elevated TNF-.alpha. and/or IL-1.beta. by administering therapeutic amounts of stearidonic acid. Further provided are methods for down-regulating TNF-.alpha. and/or IL-1.beta. and assays for determining the presence, absence, or quantity of TNF-.alpha. and/or IL-1.beta. in a subject in conjunction with a regimen of stearidonic acid administration.