It seems possible to evaluate language proficiency as behavioral ability by: (1) observing authentic language behavior, (2) examining the tacit knowledge that underlies language behavior or testing specific tasks based on capabilities that are linked to implicit knowledge of a language, and (3) testing the acquired explicit knowledge, such as use of grammatical rules. A test was administered to foreign nationals in the Netherlands who were applying to teach their native languages and cultures to preschoolers. The test, intended to measure the first two factors, consisted of an oral proficiency test of authentic language behavior, a standard multiple-choice test, a multiple-choice test of orthography and morphology, and a cloze test. Analysis of the data found similar results for measurement of language proficiency by evaluating language behavior and by testing implicit knowledge. Problems with the orthography subtest emphasized the need to consider language background when evaluating proficiency. (MSE)