Sociolinguistics at Penn focuses on linguistic variation and change in progress. Research in this field looks into the causes of linguistic change, such as social factors and contact with other languages, and has implications for all other subfields.

Since 1970 Penn has led the world in sociolinguistics, by which we mean the technical study of linguistic variation in society and its complex relation to language change in progress. , the director of the Linguistics Laboratory, began this line of research some thirty years ago; his efforts and those of , our specialist in multilingualism, contact phenomena, and creoles, have produced a series of graduates who now hold major positions in sociolinguistics all over the world. This type of study has also informed work in virtually all other subfields.

Labov has published the second volume of his Principles of Linguistic Change in 2001 (Blackwell) and more recently his Atlas of North American English (Mouton de Gruyter). Labov is also proceeding with sociolinguistic research under two National Science Foundation grants. One project seeks to investigate the ability of native speakers to perceive and evaluate the range of frequencies of variants that have been found in studies of speech production.

Labov is also conducting outreach to the community at large. Working with the Drew School in West Philadelphia, he and his coworkers have embarked on a large-scale project to improve elementary students' reading skills, making use of the findings of sociolinguistics. The primary thrust of the project is the training of reading tutors. Partly to that end, they have produced an Individualized Reading Manual whose modules focus on specific conceptual and processing difficulties that students encounter in learning to read.

Sankoff is in the third year of a major NSF-funded project, "Language Change Across the Lifespan." This project addresses systematically, for the first time, the extent to which adult native speakers modify their existing grammars in response to ongoing change in their speech communities; the data are three longitudinal corpora of Montreal French. Sankoff has already achieved significant and unexpected results. She also continues to work on language contact in Montreal and on Tok Pisin (in Papua New Guinea).