We conducted a natural field experiment to further our understanding of the economics of charity. Using direct mail solicitations to over 50,000 prior donors of a non-profit organization, we tested the effectiveness of a matching grant on charitable giving. We find that the match offer increases both the revenue per solicitation and the response rate. Larger match ratios (i.e., $3:$1 and $2:$1) relative to a smaller match ratio ($1:$1) had no additional impact, however. The results provide avenues for future empirical and theoretical work on charitable giving, costbenefit analysis, and the private provision of public goods.