Light pollution is a term used to describe the negative consequences of excessive, scattered and intrusive artificial night light, which ultimately leads to the loss of darkness and the night as an important biological factor. We distinguish “astronomical light pollution” which prevents astronomical observations because of increased night sky brightness that lowers the contrast with the observed objects (stars, asteroids and such), and “ecological light pollution” which alters or interferes with natural light regimes during the night. The aim of this seminar is to give a short review of the negative consequences of light pollution that were discovered so far, with emphasis on taxa such as sea turtles, migrating birds, moths and bats, because they showed the most severe side effects. The negative consequences on plants and humans were described separately, mostly because there was little research on plants, and because the full list of health problems associated with exposure to light during nighttime was just recently discovered, the most severe being the increased risk of breast cancer development. Even though it may seem that a lot of work has been done these previous years, there is a lot that still needs to be researched, and so far we have only gotten a glimpse of the real extent of the problem.