Abstract: Thysanoptera species variation, their population densities, and their natural enemies in chemically treated and untreated vineyards in Alaşehir district Manisa province, the most important grape production center in Turkey, were determined in 2004 and 2005. Among the phytophagous species, Mycterothrips albidicornis (Knechtel) and M. tschirkunae (Jachontov), Rubiothrips vitis (Priesner), Thrips tabaci Lindeman, Frankliniella occidentalis (Pergande), and Tenothrips frici (Uzel) were the most frequent. M. albidicornis, M. tschirkune, and T. frici populations were found in untreated vineyards, while R. vitis and F. occidentalis populations, which are the most important species in Turkish vineyards, were found to be more abundant in the chemically treated vineyards. It was observed that the T. tabaci population can be present at high population densities in the chemically treated as well as in the untreated vineyards, depending on the year. When the total numbers of all of the thrips species obtained in the two years were compared for four experimental vineyards, it was determined that the thrips populations in the chemically treated vineyards were higher than in the untreated ones. The population densities of their natural enemies – some species of spiders, Chrysoperla carnea (Stephens) (Chrysopidae), the mite Anystis baccarum (L.) and, the entomophagous thrips Scolothrips longicornis Priesner, Aeolothrips collaris Bagnall and A. intermedius Priesner were found. The Araneidae spiders, S. longicornis, A. collaris, A. intermedius and A. baccarum (Anystidae) were found more often in the chemically treated vineyards, while C. carnea was more frequently found in the untreated vineyards.