Low cost, improved cook stoves can potentially provide multiple benefits for local environments and climate through net reduction in fuel use and emissions from use of biomass fuels compared to traditional stoves. However the fuel efficiency of improved cook stoves has undergone limited in-field evaluation. In this study, we assessed the effectiveness of rocket mud stoves (RMS) in reducing fuelwood use in a rural community in Kenya. Using both cross-sectional and longitudinal (before-after) study designs, we conducted two-day kitchen performance tests in 145 households and 37 households, respectively. Fuel consumption was 5.4 kg d(-1) in the rocket stove group and 6.7 kg d(-1) in the three-stone stoves group. After we accounted for number of people cooked for, cooking duration and fuel moisture, EMS use was associated with 1.6 kg d(-1) (95% CI: 0.6, 2.7) lower fuel use relative to three-stone stoves in the cross-sectional sample, and 2.2 kg d(-1) (95% CI: 1.0, 3.3) lower fuel use in the longitudinal sample. Our data suggest that simple wood stoves like rocket mud stoves could ease the burden of fuelwood collection for rural households, and potentially address social and local environmental consequences of fuelwood collection. (C) 2013 Elsevier Ltd. All rights reserved.