The Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway is a pleiotropic cascade essential to cytokine and growth hormone receptor signaling. Signaling through the JAK/STAT pathway is important for the kidney's response to injury in disease. Pang et al. confirm that activation of STAT3 mediates renal fibrosis in the unilateral ureteral obstruction experimental model.