Motivation and Hypothesis: Asthma affects ~17 million people in the USA (~8% of the population) and proportionately more in other countries worldwide. Airway diseases such as asthma are triggered by inflammation and mediated by inflammatory cytokines, including TNFα and IL-13. After exposure to inflammatory cytokines, the airways become hyperreactive due to an enhanced cytosolic Ca2+ ([Ca2+]cyt) response of airway smooth muscle (ASM) to agonist (e.g., acetylcholine – ACh) stimulation leading to increased force generation. The Ca2+ sensitivity of force generation is also increased by TNFα and IL-13. In addition to these changes in contractility, inflammatory cytokines induce dynamic remodeling of the cytoskeleton in ASM, which affects the transmission of force to the extracellular matrix. We hypothesized that the level of intrinsic (basal) force in small human airways also contributes to hyperreactivity. Methods and Results: Human bronchi (segments – 4-5 mm in length and 1-2 mm in diameter) were obtained from surgical lung specimens in accordance with procedures approved by the Mayo Clinic Institutional Review Board. Tissues were obtained incidental to surgery and were discarded by the surgical pathologist. All tissues were immersed in ice-cold HBSS and ~5th generation bronchi were freed from adherent tissue using a dissecting microscope. Studies were performed on both epithelium-intact and epithelial-denuded bronchi. Human bronchi were obtained from surgical specimens as described above. Bronchial rings were mounted vertically between two stainless steel wire supports, one fixed the other attached to an isometric force transducer. The organ baths contained 10 ml physiological salt solution maintained at 37oC and bubbled continuously with 5% CO2 in O2, pH 7.4. Intrinsic force in was estimated by reducing extracellular [Ca2+] to zero and was found to be ∼50% of the maximal force elicited by 10 μM ACh. Intrinsic force was also revealed by β-adrenergic activation (isoproterenol), non-specific cationic channel blockade (La3+) or L-type voltage gated Ca2+ channel blockade (nifedipine). Atropine, indomethacin, AA-861, or pyrilamine did not affect intrinsic force. Chelating intracellular [Ca2+] using BAPTA-AM reduced intrinsic force, while blocking voltage-dependent Ca2+ channels with ω-conotoxin had no effect. In a separate study in intact human airway smooth muscle strips, we measured intracellular [Ca2+] using either Fura-2 or Fluo-3. These studies verified the impact of each experimental condition on intracellular [Ca2+]. In additional studies on intact and permeabilized human airway smooth muscle strips, we found that cytochalasin D-induced inhibition of actin polymerization also reduces intrinsic force, while increasing basal ATP consumption. Conclusions: These results indicate that intrinsic force is primarily dependent on the level of basal intracellular [Ca2+] but is also affected by factors that influence Ca2+ sensitivity and cytoskeletal remodeling. We speculate that intrinsic force is a fundamental property of ASM, and that an increase in intrinsic force via elevated basal intracellular [Ca2+], increased Ca2+ sensitivity or altered cytoskeletal remodeling may at least partially underlie increased airway resistance and airway hyperresponsiveness associated with asthma.