One of the earliest preserved Sanskrit works on Perso-Arabic (Tājika) astrology, the thirteenth-century Karmaprakāśa of Samarasiṃha (also known as the Manuṣyajātaka, Tājikatantrasāra or Gaṇakabhūṣaṇa), is examined with particular attention to subgenre, distinctive content and likely Arabic-language sources. On the basis of a comparison of the extant text of the Karmaprakāśa with excerpts attributed to Samarasiṃha by later Tājika writers, conclusions are drawn with regard to other works, now lost or misattributed, by the same author.