This study attempts to explore behavioral characteristics of international tourists visiting Istanbul in guided tours, and to examine the differences and similarities among tourists of different nationalities using data provided by Turkish tour guides. Data were collected utilizing a survey site designed for research for Turkish tour guides working in Istanbul, Turkey. The results suggest that there are three underlying dimensions of tourists' behavior during guided tours, namely, shopping, activities, and social interaction. Significant differences are observed among seven nationalities. Pair comparisons of the groups belonging to the three dimensions are conducted for the purpose of revealing similarities and differences. The Japanese are found to be the most distinct tourist group in comparison to others. Finally, conclusions and implications are discussed at the end of the study.