Labor supply models are sensitive to the measures of health used. When self-reported measures are used, health seems to play a larger role and economic factors a smaller one than when more objective measures are used. While this may indicate biases inherent in using self-reported measures, there are reasons to be suspicious of more objective measures as well. A statistical model incorporating both self-reported and objective measures of health shows the potential biases involved in using either measure or in using one to instrument the other. The model is initially unidentified, but incorporating outside information on the validity of self-reported measures confirms fears about both the self-reported and objective measures available on such data sets as the Retirement History Survey or the National Longitudinal Survey of Older Men.