Firefighter boots may be composed of rubber, lighter leather, or ultralight fabric. Boot soles can be stitched (less flexible) or cemented or bonded (more flexible). A five to 12% increase in oxygen consumption per kg of weight added to the foot has been observed; however, this increase may depend on boot weight and sole type. PURPOSE: To determine the effects of fabric/stitched sole (FS), leather/stitched sole (LS), leather/cement sole (LF) and rubber/bonded sole (RF) boots on firefighters' metabolic and respiratory variables during simulated firefighting tasks. METHODS: Fourteen women and 14 men, wearing full turnout clothing and equipment and one of four pairs of boots, climbed up and down a 3.7-m ladder for five minutes at 25 rungs per minute and then walked for five minutes at 0.57 mĚsec-1 while stepping over four obstacles and carrying a 9.5-kg hose. Minute ventilation (VE), oxygen consumption (VO2 and VO2/kg), CO2 production (VCO2), and heart rate (HR) were measured, and minute-five data were used for analysis. Comparisons of boot weight and sole type were made using ANOVA with repeated measures. RESULTS: During ladder climbing, boot weight had a significant effect (P < 0.05) on VE, VO2 and VCO2 (*). There were significant effects (P < 0.05) of both boot weight and sole type for VO2/kg (**). During obstacle crossing, boot weight had a significant effect (P < 0.05) on VE, VO2 and VO2/kg (*). There were significant effects (P < 0.05) of both boot weight and sole type for VCO2 (**). CONCLUSION: There were significant effects of boot weight (4 - 6% increases per kg increase in boot weight) during both ladder climbing and obstacle crossing, which were mitigated by sole type for VO2/kg (2% decrease, ladder climbing) and VCO2 (6% decrease, obstacle crossing).