The new Classification and Diagnostic Criteria for Diabetes Mellitus (DM), prepared by a group of experts from the American Diabetes Association is presented and analyzed. On an etiopathogenic basis, it designates Insulin Dependent and Non Insulin Dependent as Type 1 and Type 2 respectively. It specifies DM having specific known causes. It maintains Gestational Diabetes and Glucose Intolerance and adds the Impaired Fasting Glucose Condition. It recommends fasting plasma glucose for search and diagnosis, and lowers the level to <FONT FACE=Symbol>³</font>126 mg/dl instead of <FONT FACE=Symbol>³</font>140 mg/dl, due to its association with chronical complications of DM. It mantains the diagnostic criteria of random and post charge glycemia <FONT FACE=Symbol>³</font>200 mg/dl. It does not alter the glucose intolerance figure (140ó200 mg/dl in OGTT) and introduces fasting abnormality <FONT FACE=Symbol>³</font>110 and &lt;126 mg/dl. It encourages the search with fasting glucose every 3 years in individuals aged over 45, and at more frequent intervals in younger individuals with high risk factors. Analysis of the report allows to conclude that, although the classification does not introduce any significant change in daily clinical use, its pathogenic orientation makes future innovations possible. The preferential use of fasting glucose <FONT FACE=Symbol>³</font>126 mg/dl for diagnosis of DM has theoretical basis and practical advantages. Identification of individuals with impaired fasting glucose allows to detect, in a simple manner, a high risk group in which to start preventive measures. However, there is a percentage of cases which are not diagnosed by fasting glycemia, but are diagnosed by OGTT, therefore the latter should not be discarded.