This study combines a descriptive and theoretical presentation of KTnni, a Gur language of northern Ghana. It presents an Optimality Theory analysis of the entire phonological system. The description of noun morphology includes the noun class system, the reduplicative agentive noun construction, noun-adjective complexes, and derived nouns. Verbal morphology is comprised of various aspectual suffixes. The phonological description is separate from the formal OT analysis in order to facilitate use by those with descriptive interests as well as theoretical. The book includes major sections on consonants, vowels, and tone. It also includes a brief syntax sketch, co-occurrence restrictions, phoneme frequency counts, phonetic measurements of segment durations and vowel formants, as well as seven appendices of data. Some specific notes of interest: Some phonology is limited to only certain noun classes, A pervasive 9-vowel ATR vowel system is analyzed, to which dipthongization has an integral tie, Some vowels assimilate only across consonants with the same place feature, The existence of [H!H] on a single TBU is documented, Tonal perturbations demand four different underlying representations for different nouns which all have a surface [LH], True tonal polarity, distinct from dissimilation, is argued for, Two cases of syntax-phonology interface occur in the vowel system. Michael Cahill received his Ph.D. in Linguistics from The Ohio State University in 1999. Having worked with SIL since 1982 and worked on-site with the KTnni-speaking people 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 serving as the International Linguistics Coordinator of SIL.