The processes involved in assessment in clinical psychology are diverse and complex. Clinical assessment plays an important role in what has been called the Health-Disease process, especially in relation to mental health. The training of professionals in this area of health must be considered in a comprehensive and dynamic way, taking into account the social environments in which the people who request psychological consultation are immersed. One of the professional competences is assessment, which leads to another vital process in clinical practice: therapeutic intervention. Ethical aspects must always govern the behaviour, attitudes and values of the psychological discipline and of professionals in training and under the supervision of their clinical work and their own personal processes of personal psychotherapy.