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 formula presented (formula presented ), black carbon (BC), and carbon monoxide (CO) at baseline and 3-, 6-, 12-, 18-, and 24-months post randomization. RESULTS: Baseline formula presented (kitchen area concentrations formula presented vs. formula presented ; personal exposure formula presented vs. formula presented ), CO (kitchen formula presented vs. formula presented ; personal formula presented vs. formula presented ), and BC (kitchen formula presented vs. formula presented ; personal formula presented vs. formula presented ) were similar between control and intervention participants. Intervention participants had consistently lower formula presented concentrations at the 12-month visit for kitchen (formula presented , and formula presented ) and personal exposures (formula presented , and formula presented ) to formula presented , 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 formula presented , BC, and CO kitchen mean concentrations of formula presented , and formula presented and personal exposures of formula presented , and formula presented , respectively), and average reductions were present among intervention participants even after free fuel distribution stopped (24-month visit formula presented , BC, and CO kitchen mean concentrations of formula presented , and formula presented and personal exposures of formula presented , and formula presented , 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.