We describe a small telescope system, the Berlin Exoplanet Search Telescope (BEST), dedicated to the search for planetary transits of Jupiter-sized planets on close-in orbits. This system consists of a commercial 20 cm telescope equipped with a 2048 x2048 pixel CCD. Observations have been performed for almost 2 years, including a commissioning phase and regular observations. Planetary transit candidates have been found and followed further with radial velocity measurements. One example is discussed here: transit events detected around GSC 3566-1556 have been identified as being caused by a binary system consisting of a G0 V primary orbited by an M star. The radii of both stars have been determined.