In this research, it was aimed to develop an instrument for determining problematic internet usage of university students. Factorial structure of the data collected from 1658 university students revealed three factors. Of these, the first factor is called negative consequences of the internet and accounted for 25.36% of the variance, the second factor is called social benefit /social comfort and accounted for 14.62% of the variance, and the third factor is called excessive usage and explained 8.98 % of the variance. All three factors consisting of 33 items accounted for the 48.96% of the total variance. It was found that the scale was able to discriminate problematic internet use with respect to the time spent on the internet and individuals' perception of themselves as the internet addicts. The correlation between the scale and the Davis's Online Cognitive Scale-Turkish adaptation (Keser Ozcan ve Buzlu, 2005) was found as 0.61. Internal consistency coefficient of the scale (alpha) was found to be 0.94. Item total correlations ranged between 0.31 and 0.70 (p less than 0.001). Test-re-test reliability coefficient was found to be 0.81 and split half reliability coefficient was found to be 0.83. Thus, the scale called "the Problematic Internet Usage Scale" was developed.