Investigation commissioners (caifangshi 采訪使, also written 採訪使), full title investigation and supervisory commissioner (caifang chuzhi shi 采訪處置使) were high civilian officials with a temporary appointment. The title was in use during the Tang period 唐 (618-907), but first appeared during the Jin period 晉 (265-420), when Shi Chong 石崇 (249-300) was investigation commissioner of the remote commandery of Jiaozhi 交趾 (today in Vietnam). During the early Tang it was called anchashi 按察使, but in 714 renamed ancha caifang chuzhi shi 按察采訪處置使. In 713 the empire was divided into fifteen circuits (dao 道), in each of which an investigation commissioner was appointed. From that date on the short form caifangshi was used.
The duties of this office were similar to that of regional inspectors (cishi 刺史), namely disciplinary supervision and the control of accurateness of prefects and magistrates. Ni Ruoshui 倪若水 (d. 719), for instance, was concurrently regional inspector and investigation comissioner of the prefecture of Bianzhou 汴州. In later times the office holders were concurrently appointed personnel evaluation commissioners (chuzhishi 黜陟使). From 750 on the range of duties was restricted to the evaluation of officials, and interference into the administration forbidden. Eight years later the office was renamed surveillance and supervisory commissioner (guancha chuzhi shi 觀察處置使, short guanchashi 觀察使), and gradually concurrently taken over by defense commissioners (fangyushi 防禦使) who where responsible for the supervision of military affairs.