Investigation Led by ZnaToKi, or Investigation Led by Experts (Russian: Следствие ведут ЗнаТоКи, translit. Sledstvie vedut ZnaToKi) was a popular 1971-1989 Soviet detective TV-series with two Russian series (2002 and 2003). Total episodes released - 24.

Main characters - investigator Pavel Znamenski, detective Alexandr Tomin and laboratory analyst Zinaida Kibrit were acting together under a group name ZnaToKi (translated as "Experts").

Song by Mark Minkov based on the lyrics Invisible Battle (Nezrimiy Boi - Our mission is both dangerous and difficult, and most invisible at first glance...) by Anatoly Gorokhov features in almost all series. It became an unofficial hymn of the Soviet Militia.

This series was the soviet version of the East German Polizeiruf 110, which also premiered in 1971.