PeptideAtlas is a web-accessible database of LC-MS/MS shotgun proteomics results from hundreds of experiments conducted in diverse laboratories, with all data processed via a uniform analysis pipeline. A total of 91 experiments on human plasma and serum are included. Using the PeptideAtlas web interface, users can browse and search the Human Plasma PeptideAtlas for identified peptides and identified proteins, view spectra, and select proteotypic peptides. Users can easily view supporting information such as chromosomal mapping, estimated abundances, and sequence alignments. Herein, the reader is instructed in the use of the Human Plasma PeptideAtlas through an illustrated exploration of cytokine receptors in plasma.