This second volume in the Studies in Language Testing series is based on research carried out for volume 1. It investigates the influence of test-taker characteristics on test performance in tests of English as a foreign language by exploring the structural relationships among these two groups of variables. The investigation was carried out in the context of constructing a theory of construct validity of EFL performance by finding explanations for individual differences among test-takers whose characteristics influence their performance. The study involved modeling data from 985 subjects from eight countries grouped into two native-language groups, the Non Indo-European group and Indo-European group. The measures of EFL test performance were the First Certificate in English, the TOEFL, the SPEAK, and the Test of English Writing.