Phosphor-converted white light-emitting diodes (pc-white LEDs) have attracted considerable attention as a new generation light source since the first commercial GaN chip was invented in 1990s. A pc-white LED can be regarded as a sophisticated system including a number of components made of a variety of materials. An understanding of the behavior of its component parts is helpful to gain a comprehensive insight of the failure of the pc-white LED itself. For this reason, issues related to materials and reliabilities of the LED key components such as LED chip, phosphor, encapsulant, lead frame, and interface are discussed in this chapter.