Attendance figures are an indicator of the popularity of zoos in society, and also reveal the levels of funding available because entrance fees and other revenues generated during visits are the main sources of funding for British zoos. However, the literature provides conflicting information on zoo attendance, and existing reports are also limited by their research designs and lack of international perspective. Therefore, it is difficult to judge how popular zoos really are, and hence there is a need for a detailed analysis of zoo attendance. To deal with this, the present article reports an analysis of worldwide zoo-attendance patterns using a large data set provided by the International Zoo Yearbook. The data show that attendance has generally declined in most world regions during the 40 year period, and was particularly marked during the 1960s and 1970s. There have been recent increases at North American and British zoos since the 1980s. More people visit zoos in Japan and the United States, and attendance patterns during the past 40 years have followed different paths in different world regions and countries. Attendance figures for zoos around the world were compared with several socio-economic variables, and the analysis revealed a positive significant relationship between a country's population size, country income and zoo-attendance figures.