The TRP (transient receptor potential) superfamily of cation channels is present in all eukaryotes, from yeast to mammals. Many TRP channels have been studied in the nematode Caenorhabditis elegans, revealing novel biological functions, regulatory modes, and mechanisms of localization. C. elegans TRPV channels function in olfaction, mechanosensation, osmosensation, and activity-dependent gene regulation. Their activity is regulated by G protein signaling and polyunsaturated fatty acids. C. elegans TRPPs related to human polycystic kidney disease genes are expressed in male-specific neurons. The KLP-6 kinesin directs TRPP channels to cilia, where they may interact with F0/F1 ATPases. A sperm-specific TRPC channel, TRP-3, is required for fertilization. Upon sperm activation, TRP-3 translocates from an intracellular compartment to the plasma membrane to allow store-operated Ca2+ entry. The TRPM channels GON-2 and GTL-2 regulate Mg2+ homeostasis and Mg2+ uptake by intestinal cells; GON-2 is also required for gonad development. The TRPML CUP-5 promotes normal lysosome biogenesis and prevents apoptosis. Dynamic, precise expression of TRP proteins generates a remarkable range of cellular functions.