This study explored the latent variables underlying C-Tests by analyzing the performance of 416 undergraduate and graduate university students majoring in English Language and Literature, English Language Teaching and English Translation in Mashhad, Iran. The C-Tests designed by Klein -Braley (1997) were changed into two other types of tests called Spelling Test and Decontextualised C-Test and administered along with the disclosed Test of English as a Foreign Language (TOEFL), a semantic schema -based cloze multiple choice item test (S-Test) and a lexical knowledge test (LKT ). The application of principal component analysis (PCA) to the responses of the participants on the three tests, i.e., C-Tests, Spelling Test and Decontextualised C-Test, revealed two components called language proficiency and direction specificity in this study. While the inclusion of the S-Test, TOEFL and the LKT in the PCA yielded the same two components, their rotation brought about the highest loadings of the included tests as well as the moderate loadings of the C-Tests on the first component, validating them as proficiency measures of language. However, they loaded the highest on the second component along with the Spelling Test and Decontextualised C-Test and thus confirmed their spelling and direction specificity. The implications of the study are discussed and suggestions are made for future research.

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