This study uses The Third International Mathematics and Science Study (TIMSS) data to compare students from Hong Kong with students from the US on the mathematics achievement and on a series of family background factors such as mothers' expectations, parental education, presence of study aids, living with different family members, and extracurricular time spent in various activities. Results indicate the following. (1) Hong Kong students outperformed their US counterparts in mathematics scores. Hong Kong has advantages in half and US about one-fifth of the family background factors. (2) Seventy-five percent of the factors are significantly associated with mathematics achievement for both countries. (3) Some of the factors influence Hong Kong and US students differently. Recommendations are made on family school partnership strategies such as engaging parents in decision-making roles in educational programs at school for Hong Kong and limiting recreational TV viewing and emphasizing value of schooling at home for the US.