Errors in the selection and technique of treatment and in the control of metabolism may still determine the fate of a diabetic after years or decades. Guidelines and pointers to indication and initiation of insulin therapy are given, including particulars of the problems of choosing the appropriate insulin and of dosage. Importance is attached to the differing times to onset of effect of the various insulin preparations, a balanced metabolic condition can hardly be attained without taking them into account. Individual peculiarities of the metabolic process may necessitate the use of special insulin combinations. Every diabetic treated with insulin should have both knowledge and possibilities of controlling the metabolism himself. Among the indications for the use of the new, highly purified chromatographed insulins, lipoatrophic dystrophy at the injection sites has recently been particularly noted.