This paper discusses the signal processing requirements for a perpendicular magnetic recording (PMR) read channel and presents performance measurements from a physical PMR channel, heads, and media. A signal and noise model of a PMR channel is described. Next, a search for partial-response maximum-likelihood (PRML) targets suited to PMR is performed. The components of a real PMR channel are described, including a modified analog front-end, differential servo mode, and an adaptive baseline-tracking loop. Finally, error rate data from a PMR spin-stand system is presented.