Number 12 in this SeriesThoracoscopy -state of the art R. Loddenkemper aa Thoracoscopy was introduced by JACOBAEUS [1], an internist in Stockholm in 1910, primarily as a diagnostic procedure in two cases of exudative (tuberculous) pleuritis. In his excellent overview "Thoracoscopy and its practical importance" JACOBAEUS [1] published his accumulated experience of thoracoscopy in all the indications which are still in 1998 the domain of pneumologists [2]. With malignant effusion, he was frequently able to differentiate between primary and secondary tumours of the chest wall, pleura, lung and mediastinum. He divided tuberculous pleurisy into different stages, studied rheumatic and nonspecific parapneumonic effusions and he performed thoracoscopy in more than 100 empyemas, many of which were nontuberculous. He also appreciated that, frequently, one could not visualize the defect in idiopathic, spontaneous pneumothorax. However, during the ensuing 40 yrs, thoracoscopy was applied on a worldwide scale almost exclusively for the lysis of pleural adhesions by means of thoracocautery ("Jacobaeus' Operation") to facilitate pneumothorax treatment of tuberculosis (TB) [3].With the advent of antibiotic therapy for TB, a generation of physicians, already familiar with the therapeutic application of thoracoscopy, began, mainly in Europe, to use this technique on a wider basis for evaluating many pleuropulmonary diseases [4,5]. Detailed descriptions of pleural disease, with emphasis on tuberculous and malignant effusions, appeared in the literature and the diagnostic potential was again verified. Concurrently, many American surgeons preferred thoracotomy and open biopsy for evaluation of these diseases.Due to technical improvements and a trend towards less invasive procedures, thoracoscopy was rediscovered by thoracic surgeons at the beginning of this decade, and termed "surgical" thoracoscopy, which is more precisely known as video-assisted thoracic surgery (VATS) [6][7][8]. Interestingly, this revival has also supported the introduction of "medical" thoracoscopy into the scope of respiratory physicians, in particular in the USA where, according to a national survey in 1994, already more than 5% of all pulmonologists were applying medical thoracoscopy [9]. In Thoracoscopy -state of the art. R. Loddenkemper. ERS Journals Ltd 1998. ABSTRACT: "Medical" thoracoscopy as compared with "surgical" thoracoscopy (which is more precisely known as video-assisted thoracic surgery (VATS)) has the advantage that it can be performed under local anaesthesia or conscious sedation, in an endoscopy suite, using nondisposible rigid instruments. Thus, it is considerably less invasive and less expensive.The main diagnostic and therapeutic indications for medical thoracoscopy are pleural effusions and pneumothorax. Due to its high diagnostic accuracy, approaching almost 100% in malignant and tuberculous pleural effusions, it should be used when pleural fluid analysis and needle biopsy are nondiagnostic. In addition, medical thoracoscopy provides st...