We estimate adults’ willingness to pay (WTP) to reduce health risks to their own or other families’ infants to test for altruism. A conjoint analysis of adults paying for bottled water found marginal WTP for reduction in risk of shock, brain damage, and mortality in the cash treatment of $2, $3.70, and $9.43, respectively. In the hypothetical market these amounts were $14, $26, and $66, indicating substantial hypothetical bias, although not unexpected due to the topic of infant health. Statistical tests confirm a high degree of altruism in our WTP results, and altruism held even when real money was involved.