Three-dimensional visualization skills are critically important to success in engineering careers. Unfortunately, studies have shown that the 3-D spatial visualization skills of women engineering students lag significantly behind those of their male counterparts. This paper examines gender differences in background and in visualization ability for students enrolled in the United States and in Brazil. Factors that seem to be significant in the development of visualization skills are presented. Gender differences and other problems in visualization skills that cross international boundaries are described. (WRM)