As the production of missile, nuclear devices and electronics grew and modern industrial technologies emerged the risk of the occupational exposure to beryllium has become increasingly common and widespread. The environmental burden of beryllium is also on the increase, not only as a result of emissions from plants producing and processing beryllium, or its alloys and compounds, but also from burning coal of higher beryllium content in some localities. This article discusses primarily the hygienic and toxicologic aspects of beryllium and its threat to human health. The following topics are included in this review: occurrence, production and uses of beryllium; its metabolism and experimental toxicology; clinical toxicology and pathogenesis of berylliosis; hygienic and epidemiologic aspects of berylliosis; berylliosis treatment and prevention. Berylliosis is here characterized as a disease combining clinical manifestations of pneumosclerosis, allergy to beryllium and, in its granulomatous form, autoimmune reactions. Importantly, the available technical means and measures can ensure that the both occupational and environmental exposure to beryllium can be kept below the established MAC values. If occasionally impossible, special preventive measures should be adopted. It is essential that all persons with allergy be prophylactically excluded from work at risk of exposure to beryllium.