The report of the Interagency Language Roundtable's invitational symposium on language aptitude testing consists of a description of the project and appendixes which include the following: (1) the symposium program and abstracts of papers; (2) a list of participants; and (3) summaries of the discussions of three working groups (on applications, research, and instrumentation respectively). The symposium was developed in response to intense interest in testing for foreign language learning aptitude among government agencies involved in foreign language training. It included individual and panel presentations by representatives of the National Cryptologic School, Federal Bureau of Investigation, Public Service Commission of Canada, Defense Language Institute, Central Intelligence Agency, National Security Agency, Army Research Institute, Foreign Service Institute, U.S. Air Force Academy and academic institutions. The presentations included these topics: aptitude tests currently in use in government agencies; cognitive abilities and foreign language aptitude; the uses and limitations of various tests in public agencies; predictors of success in intensive language learning; a new language aptitude test using an artificial language; learning styles, strategies, and aptitude; cognitive models of students' language structure based on intelligent computer-assisted instruction; the relationship between cognitive development and language proficiency; brain hemisphericity, language aptitude testing, and prediction of success in foreign language learning; and aspects of attitude, motivation, and personality in language learning. (MSE)