Today more than 18 million people live in cities which impOse an income tax, and in addition countless other people wh0 commute to these cities pay a tax on the income they earn within the city boundaries. The city income tax, once considereda novelty, now provides substantial revenue in more than 170 municipalities, including 21 cities with population of at least 100,000 individuals. Much of the expansion of the city income tax has taken place in recent years, however, with the result that it is very difficult to obtain an overall view of this tax, and even broad questions cannot readily be answered on the basis of material available today. As a first step toward understanding this small but growing facet of municipal inance, this study brings together scattered information which has been published in recent years, illing in as many of the gaps as possible with additional material obtained directly from the cities concerned.