The text analyzes Ernesto Che Guevara’s classified stay in Czechoslovakia between March and July 1966. The emphasis is placed on the cooperation that existed between the Czechoslovak and Cuban secret services. Through published studies, memoirs, interviews and Che Guevara’s files, the article provides valuable insights and dispels some of the myths surrounding a mostly unknown period in the life of the famous Argentinean revolutionary. Attention is also paid to a theoretical document which Che Guevara created during his stay in Czechoslovakia. His remarks criticizing the Soviet “road to socialism” represent the biggest legacy of Che Guevara’s stay in Czechoslovakia.