The Pimsleur Language Aptitude Battery (PLAB) was developed to predict student success in foreign language learning, or language learning aptitude, and for diagnosing language learning disabilities. It is published by the Language Learning and Testing Foundation.

The Pimsleur Language Aptitude Battery (PLAB) measures language learning aptitude. Language learning aptitude does not refer to whether or not an individual can or cannot learn a foreign language (it is assumed that virtually everyone can learn a foreign language given an unlimited amount of time). According to John Carroll and Stanley Sapon, the authors of the Modern Language Aptitude Test (a similar language aptitude test intended for older learners), language learning aptitude refers to the "prediction of how well, relative to other individuals, an individual can learn a foreign language in a given amount of time and under given conditions". The PLAB is intended for use with native English speaking students in grades 7 through 12, although it is sometimes used with students as old as 20 years.

The Pimsleur Language Aptitude Battery was developed by Dr. Paul Pimsleur, also known for the Pimsleur language learning system. The PLAB is the culmination of eight years of research by Pimsleur and his associates from 1958 to 1966, which involved the review of 30 years of published studies regarding a variety of linguistic and psychological factors involved in language learning. Pimsleur and his colleagues grouped these studies into seven research topics: intelligence, verbal ability, pitch discrimination, order of language study and bilingualism, study habits, motivation and attitudes, and personality factors. Of the seven, motivation and verbal intelligence were the clearest factors contributing to success at learning a foreign language.

Subsequent research involving students learning French at the college level, taking several different tests and subjecting the resulting data to factor analysis and multiple correlation analysis also showed motivation and verbal intelligence to be primary factors in language learning success. After field testing a preliminary version of the Aptitude Battery on secondary school students of French and Spanish, Pimsleur and his associates identified verbal intelligence, motivation and auditory ability as the three most significant factors in predicting success at learning a foreign language. They developed seven subtests that would measure these three factors.

After testing the seven subtests, with the support of the Ohio State University Research Foundation, the PLAB was finalized by adding a part where the examinee indicates his or her grade point average in four core subjects. Thus, Pimsleur used GPA as a measure of study habits, which can be very important in foreign language learning, and a good predictor of success. Thus, the four final factors contributing to language learning aptitude measured on the PLAB are verbal ability, auditory ability, motivation and study habits.

1965–66, a study was conducted to calculate the predictive validity of the PLAB. Forty-one schools in thirteen different states participated in the study, which administered the PLAB to students in grades 7, 8, and 9 at the beginning of the school year. The students' final grades in a beginning language course were used to calculate the validity of the PLAB and provide statistical norms and expectancy tables.

The final version of the PLAB contains six parts (Pimsleur, et al. 2004), each one testing different aspects of the four predictive factors (verbal ability, auditory ability, motivation and grade point average):

Parts 1 and 2 are not aptitude measures. Part 1 is a measure of study habits and Part 2 is measure of motivation. Both study habits and motivation correlate with success in foreign language study. Depending on the teacher's motive in testing language aptitude, these parts could be deleted, or they could be translated to the student's native language. Therefore, the PLAB could be used with students whose mother tongue is not English but whose proficiency in English is high enough to take the test.