Multiple traits of language proficiency as well as test method effects were concurrently analyzed to investigate interrelations of construct validity, convergent validity, and discriminant validity using multitrait-multimethod (MTMM) matrices. A total of 585 test takers' scores were derived from the field test of the "Pearson Test of English Academic". An MTMM confirmatory factor analysis model was parameterized using 4 traits and 3 assessment methods. The 4 traits included "listening", "reading", "speaking", and "integrated skills", while the 3 methods included "prescribed" multiple-choice responses, "constructed" responses, and "summarized" responses. The trait factor loadings were systematically greater than those of methods, providing evidence that the indicators were strongly related to their latent constructs, after adjusting for the method effects. The results showed robust convergent validity, moderate discriminant validity, and insignificant method effects. Implications are discussed. (Contains 5 tables, 3 figures and 2 notes.)