Several aspects of the new biological revolution in contemporary psychiatry are examined. The process originated around the mid-70's. The clinico-nosological bases, provided by advances such as DSM-III and the work on ICD-10 are described, as well as the most recent laboratory accomplishments: neuroendocrine tests and neuro-radiological techniques. These events are all analyzed from a Latin American perspective, which will be more extensively elaborated on in the second part of the paper.