The possibility of interference effects between language systems has militated against the inclusion of foreign-language programs in the primary grades. Yet foreign-language instruction is operating under major federal subsidy, and evidence coming from several professions suggests that such learning would be more effective if begun in early childhood. Authorities in the fields of child development (Gesell & Ilg, 1961), neurology (Penfield, 1964; Glees, 1962), linguistics (Haugen, 1961), and education (Andersson, 1960) recommend that second-language learning be initiated no later than the beginning of formal education. Other educators disagree (Dickinson, 1961; New York State Education Department, 1962), contending the earliest feasible period for foreign-language instruction to be during the eight-to-nine age range. In the schools of this country, the latter point of view has prevailed. A major concern of curriculum specialists is second-language interference with beginning reading in the native language, and hence, with general school achievement. Underlying this concern are the results of research on bilingualism, some of which have indicated possible language deficit from the coexistence of two languages in a single nervous system (Mitchell, 1937; Smith, 1939, 1949; Darcy, 1952). Generalization from the bilingualism research to the present issue is of questionable validity, however, due to dissimilarity of both the sources and the conditions of interference. Studies of bilingualism deal with interference between two parallel (two oral, or two written) codes, where there has been long exposure to both languages. With primary foreign language programs, concern is with interference from the oral code of a second-language system to the written code of the first, under comparatively limited exposure conditions.