The Trends in International Mathematics and Science Study is a complex assessment of student achievement involving over 40 countries. The TIMSS-2003 study included two populations of students-population 1 (students of grade 4) and population 2 (students of grade 8) and two subjects (mathematics and science). One of the goals of international studies, like TIMSS, is to establish valid and reliable country's scores for achievement, in both subjects, so that to compare either background, or context variables between countries. The achievement results from the TIMSS-2003 study, provide an opportunity for a closer investigation of similarities and differences between countries. The first procedure used in this analysis was to find a two-way matrix of residuals which are the differences between the observed and expected proportions of the correct answers. The second procedure was to cluster countries according to similarities and differences in response patterns across items. It was found in previous TIMSS studies that some countries have relatively strengths in some items and some countries have weaknesses in other items. The focus of this study is on the 25 countries which participated in Population 1. Data support the view that cultural factors are influential factors that must be considered in mathematics and science education.