In general, studies on gender and mathematics show that the advantage held by boys over girls in mathematics achievement has diminished markedly over the last 40 years. Some researchers even argue that gender differences in mathematics achievement are no longer a relevant issue. However, the results of the Trends in Mathematics and Science Study of 2003 (TIMSS-2003), as well as the participation rates of girls in (advanced) mathematics courses, show that in some countries, such as the Netherlands, gender equity in mathematics is still far from a reality. Research on gender and mathematics is often limited to the relationship between gender differences in attitudes toward mathematics and gender differences in mathematics achievement. In school effectiveness research, theories and empirical evidence emphasize the importance of certain school and class characteristics (e.g., strong educational leadership, safe and orderly learning climate) for achievement and attitudes. However, there is little information available at to whether these factors have the same or a different influence on the achievement of girls and boys. This study used the Dutch data from TIMSS-2003 to explore the relationship between school- and class characteristics and the mathematics achievement and attitudes for both girls and boys in Grade 4 of the primary school. The explorations documented in this paper were guided by a conceptual model of concentric circles and involved multilevel analyses. Interaction effects with gender were assessed for each influencing factor that turned out to have a significant effect. The results of these analyses provide additional insight into the influence that non-school-related and school-related factors have on the mathematics achievement and attitudes of girls and boys. (Contains 1 figure and 6 tables.)