Issues of Modernism draws from the rich archive of little magazines of the avant guerre in order to examine the editorial intervention that shaped the emergence of modernism in their pages. Beatrice Hastings of The New Age deployed modernist techniques both in her fiction and in her editorial practices, blurring the line between text and context in order to intervene forcefully in the aesthetic and political debates of her age, crucially in the ongoing debates over women's suffrage. The first chapter follows her emergence as an experimental modernist writer and editor, showing how she intervened in the public sphere via pseudonyms and anonymous writing. When Roger Fry's exhibition, Manet and the Post-Impressionists, became the scandal of the London art world in late 1910, she used the debate over its value as an impetus to write experimental fiction that self-consciously drew from post-impressionist techniques. She continued to develop and use these techniques through the following years. The second examines her career in 1913, during which she continued to develop her modernist fiction in counterpoint to her political interventions and satires. The third chapter turns to Dora Marsden, contextualizing her developing editorial techniques from The Freewoman to The New Freewoman, and into The Egoist. This chapter demonstrates that Marsden saw seriality as a way to mitigate language's essential unreliability, a turn that made her journal a natural home for modernist experimentation. The final chapter examines H.D., a poet whose work and reception were deeply influenced by editorial decisions. Her use of complex serial poetics was overshadowed by the rhetoric of imagism in Harriet Monroe's Poetry magazine, a circumstance that had long-lasting repercussions on the evaluation of her work. Each of these case studies involves modernist texts that shaped, and were shaped by, their periodical context.