This book describes the sound system of Mono, a Banda language of the Democratic Republic of the Congo. Morphology and acoustic phonetics are discussed in order to inform the phonological analysis. Several interlinear texts and a wordlist are included. Notable features of the Mono sound system include: A phonemic bilabial flap with velarization, An eight-vowel system with fewer front vowels than back vowels, A three-level tone system that includes tonal morphemes, a tonal melody on some locative adverbs, and tonal polarity on morphologically complex prepositions, Labialization and palatalization realized as o̯ and e̯, respectively, that can accompany (among other segments) h and ʔ, Echo vowel epenthesis causing a /CLV1/ underlying syllable pattern to realized as [CV1LV1], Prothetic augmentation of subminimal nominal roots, including overapplication that results in a non-surface-apparent opacity effect, and Leftward vowel feature spreading subject to implicational restrictions. Kenneth Olson received his Ph.D. in linguistics in 2001 from the University of Chicago. He has worked with SIL since 1989 and has had an ongoing research program on the Mono language since 1994. He has taught at the University of Oregon, the Faculté de Théologie Evangélique de Bangui, and the SIL European Training Programme. He is currently the Associate International Linguistics Coordinator for SIL and an adjunct associate professor at the University of North Dakota.