A study of the effects of learning Swedish as a third language on the previously-learned English of native Finnish-speaking students examined 10,000 English-language school-leaving examinations of Finnish students for possible examples of Swedish influence in vocabulary, grammar, and word order. The examinations were those graded by a native Swedish-speaker during a 7-year period. It was hypothesized that learning Swedish, a language similar to English, would influence students' knowledge of English. Few examples of grammatical influence were found except for word order errors, many of which could be the result of interaction between Finnish and Swedish. The clearest examples of probable Swedish influence on word order were found in subject-verb inversions. Two major Swedish lexical influences were found, one in which formal similarity between existing Swedish and English words led to a negative influence on the learner, and another in which the learner's search for an individual English lexical item activated a Swedish item. The data support a hypothesis of non-native language transfer to the other non-native language being learned. Such transfer differs from native-language influence. (MSE)