Using data from the Trends in Mathematics and Science Study (TIMSS) 2003, this paper examines the problem-solving achievement of Grade 8 students in the countries that participated in the study. Data from TIMSS 2003 were used to create a new problem-solving scale, primarily based on the special, multi-part problem-solving tasks in mathematics and inquiry tasks in science. The work builds on a development project recently completed by the TIMSS and PIRLS International Study Center to create scales for the TIMSS 2003 mathematics cognitive domains. This study capitalizes on the TIMSS design, whereby students respond to both mathematics and science items in the same test booklet. The problemsolving achievement results for the Grade 8 students overall and by gender are compared to their mathematics and science achievement generally.