This manuscript is intended for various medical specialists, as well as lawyers dealing with «medical» cases. The purpose of this review was updating, supplementing and systematizing knowledge in constitutional, legal and medico-organizational issues of medical care including resolving the issue of appropriate or inappropriate medical care. The author analyzes the criteria verifying the concept of appropriate or inappropriate medical care. Certain legal and medical-organizational concepts for assessment of medical care and its effectiveness are reported: «indications for medical intervention (non-intervention)», «medical error», «complication of the underlying disease», «medical care defect», «iatrogenia», «iatrogenic pathology», etc. An algorithm for determining the complications of the underlying disease, medical care defects and iatrogenic complications, as well as principles of correct formulation of diagnosis are proposed.