This thesis analyzes the factors that determine the portfolio investments to Turkey in the period from 1989:04 to 2008:12. The factors that are examined are budget balance, current account balance, nominal exchange rate between the Turkish Lira and the US dollar, Turkish domestic interest rate, US 3-months Treasury Bill rate, annual inflation rate in Turkey and ISE 100 Index. A Vector Autoregressive Model is used for the purpose of examining the impacts of these variables on the level of portfolio investments to Turkey. The results of the model show that the portfolio investment in Turkey was affected positively by domestic interest rates and negatively by ISE 100 Index in the period before 2001. On the other hand, it is affected positively by exchange rate and US interest rate in the post-crisis period. It is also found that current account deficit affect portfolio investments negatively.