Many service occupations, such as bartenders, doormen, hotel maids, parking valets, and restaurant servers, commonly receive tips, while others, such as accountants, bank tellers, copy machine operators, doctors, and lawyers, are rarely if ever tipped. What differentiates these sets of services? Why are some occupations more likely to be tipped than others? This chapter seeks to answer these questions. It reviews evidence that occupational tipping norms are not arbitrary, but reflect the effects of occupational characteristics on consumers’ motivation to tip and on firms’ and workers’ willingness to let them do it.