Investigators of first language attrition, early bilingualism and child second language learning have found common ground on a number of important points. The present review of the research will show that the study of unevenness in the early development of two languages reveals more clearly how the critical problems for future research on bilingualism should be framed. The convergence of the above mentioned fields of study will contribute greatly to this important reflection and re-assessment. In addition, clarity on the question of balanced and non-balanced bilingual development is important for understanding how the faculty of language guides acquisition in all circumstances. (Contains 1 table and 1 figure.)