This article traces the history of Jack London’s business relationships with The Cosmopolitan magazine, which are reconstructed on the material of the scientifi cally commented The Letters of Jack London (1988). In this relationship London originally acted as an independent writer, who was attracted by the maximum royalties paid by The Cosmopolitan, then he began writing by request of the magazine’s editors, and fi nally signed a permanent contract with them, in which, contrary to his expectations, he was forced to perform the functions of a literary day-labourer. It was shown that the editorial board of The Cosmopolitan largely predetermined the genre, topic, style and content of Jack London’s writings in favor of the market demand and the tastes of its audience. This infl uence became especially signifi cant in the last third of the writer’s career, in 1910–1916. Not only did the editorial interference go against the grain with London, it fairly led to the deterioration of his literary work. In late years he was receiving criticism that would be fairer to be addressed to his patrons – editors R. Phillips, E. Sisson and the owner of the magazine W. R. Hearst, who forced the writer to choose popularity over art. Among such commissioned and adapted to the tastes of the readers of The Cosmopolitan are the following works by J. London: the collection of short stories Smoke Bellew (1912) and the novels The Mutiny of the Elsinore (1914), The Star Rover (1915), The Little Lady of the Big House (1915). It should be noted that by signing the exclusive contract with The Cosmopolitan London fell into a dependent position: since he could not publish his works in other magazines and depended on regular cheques from The Cosmopolitan, he had to write only what interested its editors.