Two devastating earthquakes occurred in Turkey, one on August 17 and the other on November 12, 1999. The magnitudes were 7.4 and 7.2 respectively. The epicenter of the first earthquake was located near Golcuk, a town near Kocaeli province, 110 km from Istanbul. The epicenter of the second earthquake was in Duzce, 150 km from Istanbul. The first earthquake occurred after midnight and killed more than 15000 people. This number is obtained from an official report, while the actual deaths are expected to be more than 20,000. The earthquake was a nightmare for the whole country, and affected almost 10 cities including Istanbul. The second earthquake occurred on November 12 in the early evening, and killed about 1000 people. The affected area from the two earthquakes has a population of about 20 million, which is one third of the whole population of the country, and almost half of the Turkish economical infrastructures is located in this region. This paper gives an overview of the two devastating earthquakes, including geological background of the region, economical impacts and degrees of damages on different aspects.