This study reports the results of a nationwide questionnaire survey of 204 speech and language clinicians from 65 facilities for mentally retarded individuals. Information was requested from clinicians about which language test they used with the mentally retarded population, why they used these tests, and how often they used them. Residential and non-residential facilities reported similar purchasing patterns of language tests. Only four tests comprised 53% of all language test administrations by the respondents during the 12 month period before the survey. Also, the predominant source of knowledge about tests was reported to be university training programs. The key issue raised by this report is why clinicians say they use particular tests. The results indicate that clinicians do not agree on the function of particular tests and some of their reasons appear of questionable validity. This report raises serious questions concerning language assessment of the mentally retarded which should prove useful for clinicians and trainers in university programs in the field of speech and language pathology. (Author/CL)