Item analysis information is rarely given for English tests of children's articulation and phonology. Therefore, there is little information about the sensitivity and specificity measures of these tests. Item difficulty and item discrimination scores were derived for 199 words that were varied for phonotactic shape, syllable numbers and stress. Fifty-nine normally speaking children and 40 children with speech impairments in the age range of 2-9 years named pictures depicting the above words. Most words had satisfactory item difficulty scores indicating ease of naming. The words that best differentiated between children with and without speech impairment were monosyllabic words containing word-initial and/or word-final clusters and polysyllabic words, that is, words of three or more syllables. Disyllabic and polysyllabic words beginning with a weak syllable also seemed to be highly discriminating. Monosyllabic words with a CV or CVC shape that contained the earlier developing sounds had unacceptable measures of item discrimination. It is recommended that the use of tests that contain a preponderance of monosyllabic words with a CVC shape and the normative data derived from them be critically reviewed, especially for children aged four years and older.