This study combines a descriptive and theoretical presentation of Kɔnni, a Gur language of northern Ghana. It presents an Optimality Theory analysis of the entire phonological system. The descriptions are separated from the formal analyses in order to facilitate use by both descriptivists and theoreticians.Morphology is described, including the noun class system, reduplicative agentive nouns, noun-adjective complexes, nominal derivations, and various verbal aspectual suffixes. Major sections are included on consonants, vowels, and tone. The volume also includes a brief syntax sketch, co occurrence restrictions, phoneme frequency counts, measurements of segment durations and vowel formants, and seven appendices of data. Selected notes of interest:? Some phonology is limited to only certain noun classes.' The 9-vowel ATR vowel system and diphthongization are integrally related.' Certain vowels assimilate only across consonants having the same place feature. ? Tonal perturbations require four different underlying representations for different nouns which have a surface [LH] tone.' True tonal polarity is distinct from dissimilation.' Two cases of syntax-phonology interface are demonstrated.Michael Cahill (Ph.D., linguistics, The Ohio State University, 1999) has been with SIL since 1982, and worked on site with Kɔnni speakers from 1986 to 1993. He was a member of the LSA's Committee on Endangered Languages and their Preservation from 2001-2003, chairing it in 2003. He is an adjunct faculty member of the University of Texas at Arlington and of the Graduate Institute of Applied Linguistics and is currently based in Dallas as the International Linguistics Coordinator of SIL.