The main purpose of this study is to evaluate eleventh grade Turkish pupils' comprehension of various general chemistry concepts which in turn enables to investigate chemistry concepts which are easier and harder for students to comprehend. Examining the effect of gender and last semester chemistry course grades on pupils' comprehension of general chemistry concepts is also within the scope of this study. The sample consists of 88 students from two Anatolian high schools in the center of Isparta, Turkey. The Chemistry Concepts Inventory (CCI), that includes non-mathematical conceptual items, was administered to students in order to collect data. Results indicated that the percentage of correct responses of students for all questions ranged from 4.5 % to 75 %. Students have troubles especially with the following chemistry concepts; "Chemical formulas and equations, macroscopic versus atomic and molecular properties, solutions, chemical reactions, properties of atoms". Two-Way ANOVA results indicated that there is no statistically significant effect of gender and chemistry course grades on students' comprehension of chemistry concepts. (Contains 4 tables and 4 figures.)