Evidence converges from multiple directions to indicate that prevention or very early intervention is the correct approach to diabetic retinopathy. Preclinical studies are identifying promising drugs or classes of drugs to be added to antidiabetic treatment. Recent clinical trials were still initiated at such late stages of retinopathy that the results are not readily interpretable. The challenge for the next few years is to find ways faster than clinical trials to ascertain the relevance to human diabetic retinopathy of adjunct drugs successful in animal studies.