Forty diabetics (19 men, 21 women; mean age 54 [41-66] years) with secondary failure of sulfonylurea treatment, were assessed by questionnaire (psychological-neurological state; scale of well-being; attitude towards achievement, and psychological aspects of performance), both before and four months after being put on insulin treatment, as to the way in which they experienced and dealt with the illness. Before the onset of insulin treatment, a general decrease in performance was the predominant symptom (29 patients), while only about half of the patients declared diabetes-specific symptoms. The necessity of insulin administration was experienced by 34 patients as a severe crisis in their chronic illness. Anxiety over failure in the act of injection (30 patients), as well as fear of the consequences regarding their job (25 patients) and of restriction in the personal sphere (31 patients) were the chief reasons for their dislike of insulin treatment. Four months after starting insulin treatment these anxieties had largely disappeared. The only remaining fear was that the necessity of insulin treatment meant that a serious stage of the disease had been reached (before insulin, 36; after insulin 18 patients). It is concluded that such patients should, as part of group therapy, become active participants in the instructions given to diabetics so that other patients can profit from their experience.