In this paper, we describe a method for estimating animal population density per unit area from mark, release, recapture (MRR) data. Standard procedures are available for estimating population size from MRR data, but not density per unit area, which is often of more practical value. If data on dispersal movements are available in addition to capture/recapture records, they can be used to estimate the area over which the study population ranges. These area estimates can then be combined with MRR abundances to yield estimates of population density. As a concrete example of how these methods can be applied, we calculated population density estimates for seven MRR data sets for the screwworm, Cochliomyia hominivorax (Diptera: Calliphoridae), from Costa Rica. As a standard of comparison, we also used a different method to calculate estimates of screwworm density for five sets of USDA APHIS Screwworm Eradication Program data from Mexico. Mean densities for both sets of analyses were similar, ranging from 10 to 120 adult flies/km2. General agreement between the Mexican and Costa Rican estimates lends support to the dispersal approach we propose here. Although we have applied these methods to the screwworm as a specific example, they are entirely general and can be applied to virtually any organism for which both MRR records and dispersal data are available.