Abstract. Many developing countries with high primate diversity are still forming wildlife reserves. However, financial resources for conservation in these countries are often limited. In this paper we show that the biology of reserve design in terms of island biogeography and minimum viable populations can be compatible with measures that minimize maintenance costs, namely perimeter surveillance. Large protected areas have substantially less perimeter to patrol than many small reserves of the same total area. Likewise, circular reserves have less perimeter than square or rectangular ones. Generally, countries with high primate diversity are using desirable strategies in design of nature reserves in terms of both finances and conservation; they have relatively large reserves and large amounts of area protected in relation to country size. However, some key primate‐containing countries, such as Madagascar, Indonesia, and southeastern Brazil, require many small reserves to insure preservation of endemic taxa. Copyright © 1991, Wiley Blackwell. All rights reserved