Fuelwood scarcity creates a widespread environmental problem that places a major burden on women and children in the rural areas of developing countries. Consequently, many governments, donors and non-governmental organizations have encouraged on-farm fuelwood production and agroforestry practices. Whether, however, fuelwood from different sources can be easily substituted is an important empirical question as the degree of substitutability can depend on local markets and households' resource endowments and incomes. In this paper, we examine the substitution between three fuelwood sources among rural households in western Kenya: fuelwood collected off-farm, fuelwood produced on-farm, and that which is purchased. Using household-specific shadow prices for fuelwood and male and female wages, we find that strict gender divisions in household labor result in limited substitution between fuelwood sources. Among the implications are that programs and policies promoting agroforestry will have limited success without first addressing the structural differences in labor markets.