Abu 'Ali Muhammad Ibn Khallad al-Basri was a distinguished disciple of the Mu'tazili theologian and founder of the Bahshamiyya, Abu Hashim al-Jubba'i (d. 321/933). He is reported to have written a theological summa, Kitab al-Usul, as well as an autocommentary. None of the works of Ibn Khallad has come down to us directly, although substantial portions of his Kitab al-Usul and/or Sharh al-Usul have reached us embedded in the Kitab Ziyadat Sharh al-Usul by the Zaydi Imam al-Natiq bi-l-haqq Abu Talib Yahya b. al-Husayn b. Harun al-Buthani (d. 424/1033). The present volume contains an editio princeps of the text of the Ziyadat, based on what seems to be a unique manuscript, owned by Leiden University Library (Cod. Or 2949 [= Arab 2307]).