BACKGROUND: Household air pollution (HAP) from biomass fuel combustion remains a leading environmental risk factor for morbidity worldwide. OBJECTIVE: Measure the effect of liquefied petroleum gas (LPG) interventions on HAP exposures in Puno, Peru. METHODS: We conducted a 1-y randomized controlled trial followed by a 1-y pragmatic crossover trial in 180 women age 25–64 y. During the first year, intervention participants received a free LPG stove, continuous fuel delivery, and regular behavioral messaging, whereas controls continued their biomass cooking practices. During the second year, control participants received a free LPG stove, regular behavioral messaging, and vouchers to obtain LPG tanks from a nearby distributor, whereas fuel distribution stopped for intervention participants. We collected 48-h kitchen area concentrations and personal exposures to fine particulate matter (PM) with aerodynamic diameter ≤2:5 lm (PM2:5), black carbon (BC), and carbon monoxide (CO) at baseline and 3-, 6-, 12-, 18-, and 24-months post randomization. RESULTS: Baseline mean ½ ± standard deviation ðSDÞŠ PM2:5 (kitchen area concentrations 1,220 ± 1,010 vs. 1,190 ± 880 lg=m3; personal exposure 126 ± 214 vs. 104 ± 100 lg=m3), CO (kitchen 53 ± 49 vs. 50 ± 41 ppm; personal 7 ± 8 vs. 7 ± 8 ppm), and BC (kitchen 180 ± 120 vs. 210 ± 150 lg=m3; personal 19 ± 16 vs. 21 ± 22 lg=m3) were similar between control and intervention participants. Intervention participants had consistently lower mean ð ± SDÞ concentrations at the 12-month visit for kitchen (41 ± 59 lg=m3, 3 ± 6 lg=m3, and 8 ± 13 ppm) and personal exposures (26 ± 34 lg=m3, 2 ± 3 lg=m3, and 3 ± 4 ppm) to PM2:5, BC, and CO when compared to controls during the first year. In the second year, we observed comparable HAP reductions among controls after the voucher-based intervention for LPG fuel was implemented (24-month visit PM2:5, BC, and CO kitchen mean concentrations of 34 ± 74 lg=m3, 3 ± 5 lg=m3, and 6 ± 6 ppm and personal exposures of 17 ± 15 lg=m3, 2 ± 2 lg=m3, and 3 ± 4 ppm, respectively), and average reductions were present among intervention participants even after free fuel distribution stopped (24-month visit PM2:5, BC, and CO kitchen mean concentrations of 561 ± 1,251 lg=m3, 82 ± 124 lg=m3, and 23 ± 28 ppm and personal exposures of 35 ± 38 lg=m3, 6 ± 6 lg=m3, and 4 ± 5 ppm, respectively). DISCUSSION: Both home delivery and voucher-based provision of free LPG over a 1-y period, in combination with provision of a free LPG stove and longitudinal behavioral messaging, reduced HAP to levels below 24-h World Health Organization air quality guidelines. Moreover, the effects of the intervention on HAP persisted for a year after fuel delivery stopped. Such strategies could be applied in LPG programs to reduce HAP and potentially improve health.