The purposes of the study reported herein were to identify the common mistakes in geometry made by junior secondary school students in Hong Kong, and to compare the students' performance in geometry with their results in a logic test. A geometry test and a logic test were developed and administered to a sample of 554 students aged between 13 and 14. The students in schools with a higher level of academic achievement were found to obtain higher scores in the geometry test. In addition, a strong correlation was found between students' achievement in geometry and their fundamental logical reasoning ability. The findings offer grounds for reflection on the geometry curriculum currently in place in junior secondary schools in Hong Kong.