We describe below different components and regulators of the endosome trafficking machinery that have been associated with familial forms of PD including Vacuolar protein sorting-associated protein 35 (VPS35), some Rab proteins, LRRK2, DnaJ homolog subfamily C member 13 (DNAJC13), Synaptojanin-1 (SYNJ1), and ATPase H(+)-transporting accessory protein 2 (ATP6AP2). The gene discussed is LRRK2; the disease is Parkinson disease.