OBJECTIVE: Latent autoimmune diabetes in adults is type 1 diabetes presenting as non-insulin dependent diabetes. One feature of the selection criteria is time independent of insulin treatment. We examine the validity of this criterion. RESEARCH DESIGN AND METHODS: Patients were recruited in nine European centers, and clinicians reported on criteria for initiating insulin. All patients were tested for GAD antibodies (GADAs) in a central laboratory. We examined time to insulin treatment for GADA-positive patients in six participating centers. RESULTS: There was intercenter variation in the criteria used to initiate insulin. Median time to insulin was 16.15 months (interqartile range 6.7-25.5) in centers with GADA testing compared with 45.6 months (29.5-61.8) in centers without routine GADA testing (P < 0.002). CONCLUSION: Time to insulin should not be used to define patients with LADA because it is dependent on local clinical judgment and the use of laboratory tests for GADA.