Although formulaic language has been studied extensively from both a linguistic and psycholinguistic perspective, little is known about the relationship between individual speakers’ knowledge of collocations and their linguistic experience, or between collocational knowledge and other aspects of linguistic knowledge. This is partly because work in these areas has been hampered by lack of an adequate instrument measuring speakers’ knowledge of collocations. This paper describes the development of such an instrument, the “Words that go together” (WGT) test, and some preliminary research using it. The instrument is a multiple choice test consisting of 40 items of varying frequency and collocation strength. The test was validated with a sample of 80 adult native speakers of English. Test-retest reliability was 0.80 and split-half reliability was 0.88. Convergent validity was established by comparing participants’ scores with measures expected to correlate with language experience (print exposure, education, and age) and other linguistic abilities (vocabulary size, grammatical comprehension); divergent validity was established by comparing test scores with nonverbal IQ. The results of the validation study are then used to compare speakers’ performance on the WGT with corpus-based measures of collocation strength (mutual information, z-score, t-score and simple frequency); however, no statistically reliable relationships were found.