Articulation of mathematics and science education is advocated in the official documents of several professional organizations. To assess the benefit of curriculum integration, a national indicator needs to be developed from a correlation study of performance scores between the two subjects. In this study, a correlation analysis was conducted at the eighth grade level using international databases from the Third International Mathematics and Science Study (TIMSS) and its repetition in 1999 (TIMSS-R). The empirical results were examined over different score scales and statistical transformations. The correlation coefficient ranged between 0.61 and 0.78, suggesting that around 36% to 60% of mathematics or science performance can be accounted for by the relationship between these two subjects. (Contains 1 table and 40 references.) (Author/SLD)