This study undertook to determine the usefulness of tartrazine and benzoate challenge and dietary avoidance in the management of patients with chronic asthma. Double-blind ingestion-challenge tests were performed on separate days with lactose, tartrazine, benzoate and acetylsalicyclic acid (ASA). Of the twenty-eight subjects challenged, one responded to tartrazine and one to benzoate. Two additional subjects responded to ASA and a further eight were not tested with this material because of a definite history of sensitivity. Twenty-four subjects completed 1 month periods of observation while first on a normal diet and then while on a tartrazine-benzoate avoidance diet. No improvement occurred during the modified diet in anyone with positive challenge-tests or in all, but one, of those with a history of ASA idiosyncrasy; paradoxically, several of these subjects worsened during this period. We conclude that tartrazine-benzoate dietary avoidance was not of value in the management of the chronic asthmatic in this study, even among patients who respond to challenge with these substances or have ASA idiosyncracy.