In patients receiving long-term therapeutic or replacement corticosteroids, delayed or inappropriate adjustment of steroid dosage during intercurrent illness may be fatal. We used a questionnaire to assess current levels of patient knowledge, awareness of the need for action during intercurrent illness and the frequency with which steroid warning cards and Medic Alert pendants were carried, in 61 patients on long-term replacement corticosteroids and in 40 patients receiving long-term therapeutic corticosteroids. Only 67 of the 101 patients taking corticosteroids were carrying a steroid warning card. Eleven of the 21 Medic Alert owners wore their pendants. Only 18 of the 41 patients in the therapeutic group and 41 of the 60 patients in the replacement group would take appropriate action during an intercurrent illness (P < 0.001). Lack of patient knowledge in this important area emphasizes the need for continuing and effective education of these groups of patients during follow-up. An information sheet detailing the exact changes to be made during intercurrent illness may help reinforce verbal advice.