The experimental research of two linguists studying the grammaticality judgments of second language learners, in which the researchers tried to find evidence that second language learners can discriminate between grammatical and ungrammatical sentences on principles of universal grammar, is examined and compared with the results of studies arguing that second language learners do not have access to the principles of universal grammar. Examples are drawn from the language of Dutch and German learners of English. It is concluded that second language learners asked to give linguistic judgments will use all available sources of linguistic knowledge, including native-language intuitions and second-language knowledge, and that ungrammaticality can be identified without having to recur to either negative evidence or universal grammar. (MSE)