He joined the Socialist-Revolutionaries around the time of the Russian revolutions of 1917, and emerged as a leading dissident in the Left-Socialist Revolutionary movement.

He gained some fame as a Left SR leader, along with such figures as Spiridonova and Kamkov.

After the failure of the attempted insurrection, he went underground and became the leader of the so-called 'left-wing of Left SRs' who advocated an irreconcilable terrorist struggle against the Bolsheviks.

He established contacts with a group of underground anarchists led by Kazimir Kovalevich, and together they organized an explosion in Leontyevsky Lane on September 25, 1919.

Cherepanov was personally interrogated by the leaders of the Cheka, Feliks Dzerzhinsky and Ivan Ksenofontov.