p-type doping due to incorporation of carbon acceptors has proven to be extremely valuable for fabrication of various III-V device structures. In general, gaseous sources have proven to be more successful than elemental sources, with trimethylgallium and halocarbons such as carbon tetrachloride being the most commonly used intrinsic and extrinsic sources respectively. While both sources are capable of supplying carbon to the growth front, their behavior at the substrate surface is significantly different. This article will discuss how these differences affect the utility of each source for doping of various materials during growth by metalorganic molecular beam epitaxy. In particular, practical considerations such as interfacial abruptness, undesirable uptake of other impurities (i.e., hydrogen or chlorine), dependence of growth rate on dopant concentration, and incorporation efficiency will be presented.