To achieve an areal density of 1 terabit per square inch (1 Tb/in2) in hard disk drives, the mechanical spacing between the flying slider and the rotating disk has decreased to approximately 1 nm. With this decrease in spacing, the head-disk interface has become increasingly more susceptible to slider-disk contacts, wear, and lubricant transfer from the disk to the slider. Contamination at the head-disk interface can cause "flying stiction", flying instability, and read/write errors, leading ultimately to failure of the disk drive. It is essential to understand perfluoropolyether lubricant transfer and hydrocarbon contamination at the head-disk interface to improve the tribological performance and the reliability of hard disk drives. In this dissertation, perfluoropolyether lubricant transfer and lubricant fragmentation at the head-disk interface are investigated numerically as a function of temperature, local pressure change, and disk velocity. Molecular dynamics is used to study the effect of laser pulse peak power, pulse duration, and repetition rate on lubricant depletion. Hydrocarbon contamination at the head-disk interface is modeled experimentally by assuming a three-step mechanism for hydrocarbon contamination, consisting of evaporation, transfer, and condensation. In addition, a numerical investigation of hydrocarbon contamination at the head-disk interface is performed using molecular dynamics simulations. The results of this dissertation provide guidance in the design of perfluoropolyether and hydrocarbon lubricants to improve the tribological performance and reliability of the head-disk interface in hard disk drives.