A comparison of the standard dichotomous choice contingent valuation model to alternative modifications that explicitly incorporate respondent uncertainty is performed to estimate economic benefits of protecting critical habitat for nine threatened and endangered fish species living in the Colorado, Green, and Rio Grande River basins. The standard dichotomous choice contingent valuation model estimated a value of $268 per household, which was compared to values ranging from $50 to $330, depending on how respondent uncertainty was explicitly incorporated into the dichotomous choice model. For this data set, incorporating respondent uncertainty had the effect of increasing the goodness of fit and decreasing the standard error of estimated willingness to pay in only one of five models tested. ¿ 1998 American Geophysical Union