The cross-cultural measurement of student self-concept involves several major problems. Despite these problems, this study involved the translation and administration of a highly reliable and valid self-concept questionnaire, the Self Description Questionnaire (SDQ) to a large sample (N = 831) of Thai grade 6 and 7 students. Item analysis revealed satisfactory item-scale correlations, with few weak items. Factor analysis of item pairs produced eight well-defined factors with the same self-concept structure as had been found in five other countries. High internal consistency coefficients for each of these eight scales indicated that the SDQ possesses acceptable reliability for use with Thai children. Gender, grade and geographical location differences are discussed in the paper.