In Manchu, asymmetry between imperfect and perfect negative forms is observed.

(i) a. adnominal imperfect endings: -ra, -re, -ro

    b. negative form: -rakû

(ii) a. adnominal perfect endings: -ha, -he, -ho

     b. negative forms: -hakû, -hekû

In this talk, based on some direct and indirect evidence, I will explore the phonological forms of these negative forms, which are hidden under the orthographic forms above. In addition, the development of phonological distinction between velar and uvular consonants in Sibe, a dialect of Manchu now spoken in Xinjiang, is explored.