The increased use of electrical systems has led to significant changes in the electromagnetic environment. The extent to which large electrical systems, such as HVDC transmission networks, impinge on the environment has become a topical and even controversial issue in recent years. This article takes a look at some of the more important technical considerations as well as the consequences HVDC transmission systems have on human beings and the environment In general. The article also considers briefly what measures ran minimise the detrimental effects of HVDC transmission. It should be noted, however, that the article considers only the direct-current case; the effects of high-voltage alternating-current transmission is a separate issue and beyond the scope of this article.