The contingent valuation approach was applied to the problem of estimating the recreation benefits from alleviating congestion at Indian Peaks wilderness area, Colorado. A random sample of 126 individuals were interviewed while hiking and backpacking at the study site in 1979. The results provide an empirical test and confirmation of the Cesario and Freeman proposals that under conditions of excess recreational demand for existing sites, enhanced opportunities to substitute newly designated sites by reducing congestion results in external benefits to the remaining peak day users who do not substitute, and should be added to the recreational use benefits of new sites.