BACKGROUND: Short-term exposure to ambient particulate matter (PM) can raise blood pressure, but the underlying mechanisms are unclear. We explored whether arachidonate metabolites serve as biological intermediates in PM-associated prohypertensive changes. METHODS: This panel study recruited 110 adults aged 50 to 65 years living in Beijing, China. The participants’ blood pressure, arterial stiffness, and cardiac and endothelial function were measured up to 7 times. The serum concentrations of arachidonate metabolites were quantified by targeted lipidomics. Ambient concentrations of fine PM (PM _2.5 ), black carbon, and accumulation mode particles were continuously monitored at a station and their associations with the health indicators were evaluated. RESULTS: Interquartile range increases in 25 to 96-hour-lag exposure to PM _2.5 , black carbon, and accumulation mode particles were associated with significant increases in systolic blood pressure (brachial: 0.8–3.2 mm Hg; central: 0.7–2.8 mm Hg) and diastolic blood pressure (brachial, 0.5–1.5 mm Hg; central, 0.5–1.6 mm Hg). At least 1 pollutant was associated with increases in augmentation pressure and heart rate and decreases in reactive hyperemia index and ejection time. The serum concentrations of arachidonate were significantly increased by 3.3% to 14.6% in association with PM exposure, which mediated 9% of the PM-associated increases in blood pressure. The levels of eicosanoids from the cytochrome P450, cyclooxygenase, and lipoxygenase pathways changed with PM exposure, and those from the cytochrome pathway significantly mediated the association between PM exposure and blood pressure. CONCLUSIONS: Short-term exposure to particulate air pollution was associated with a prohypertensive change in adults, which was in part mediated by alteration of arachidonate metabolism.