This volume contains 17 papers selected from more than 100 presented at the 40th Annual Conference on African Linguistics, which took place from April 9-11, 2009 at the University of Illinois at Urbana-Champaign. The papers include Ayo Bamgbose's keynote speech and the plenaries from Brent Henderson and Lioba Moshi. The remaining papers are divided into sections on language acquisition, morphology and syntax, phonetics and phonology, and sociolinguistics and language variation.